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- Mollusca (132 754)
- Subphylum Aculifera
- Subphylum Conchifera
- Subphylum Placophora accepted as Polyplacophora
- Superclass Aplacophora
- Class Amphineura accepted as Aculifera
- Class Bivalvia (24 992)
- Subclass Autobranchia (23 278)
- Infraclass Heteroconchia (16 634)
- Subterclass Archiheterodonta (1 205)
- Subterclass Euheterodonta (11 356)
- Subterclass Heterodonta
- Subterclass Palaeoheterodonta (4 072)
- Order Trigoniida (1 482)
- Order Unionida (2 579)
- Superfamily Deccanoidoidea N. H. Shah & Patel, 2024 †
- Superfamily Etherioidea Deshayes, 1832 (148)
- Superfamily Hyrioidea Swainson, 1840 accepted as Unionoidea Rafinesque, 1820
- Superfamily Silesunionoidea Skawina & Dzik, 2011 † (11)
- Superfamily Tamesnelloidea Van Damme & Bogan, 2015 † (2)
- Superfamily Unionoidea Rafinesque, 1820 (2 417)
- Family Cumberlandiidae Heard & Guckert, 1970 accepted as Margaritiferidae J. Henderson, 1929 (1910)
- Family Hyriidae Swainson, 1840 (147)
- Family Jilinoconchidae Q.-H. Ma, 1989 † accepted as Unionidae Rafinesque, 1820
- Family Liaoningiidae J.-S. Yu & G.-Y. Dong, 1993 † accepted as Sibireconchidae C. M. Kolesnikov, 1977 †
- Family Margaritanidae Ortmann, 1910 accepted as Margaritiferidae J. Henderson, 1929 (1910)
- Family Margaritiferidae J. Henderson, 1929 (1910) (93)
- Family Monginaiidae Delvene & Munt, 2022 † (1)
- Family Propehyridellidae Iredale, 1934 accepted as Hyriidae Swainson, 1840
- Family Sancticarolitidae Simone & Mezzalira, 1997 † (1)
- Family Tegulaedontidae Van Damme & Bogan, 2015 † (3)
- Family Unionidae Rafinesque, 1820 (2 172)
- Subfamily Alasmidontinae Rafinesque, 1820 accepted as Anodontini Rafinesque, 1820
- Subfamily Ambleminae Rafinesque, 1820 (428)
- Subfamily Anodontinae Rafinesque, 1820 accepted as Anodontini Rafinesque, 1820
- Subfamily Cuneopsinae Mongin, 1963 accepted as Oxynaiini Starobogatov, 1970
- Subfamily Gonideinae Ortmann, 1916 (185)
- Subfamily Heudeaninae Modell, 1942 accepted as Gonideinae Ortmann, 1916 (1)
- Subfamily Hyriopsinae Modell, 1942 accepted as Rectidentini Modell, 1942
- Subfamily Lamprotulinae Modell, 1942 accepted as Lamprotulini Modell, 1942
- Subfamily Lampsilinae Ihering, 1901 accepted as Lampsilini Ihering, 1901
- Subfamily Leguminaiinae Starobogatov, 1970 accepted as Gonideini Ortmann, 1916
- Subfamily Limnoscaphinae Lindholm, 1932 accepted as Rectidentini Modell, 1942
- Subfamily Margaritaninae Ortmann, 1910 accepted as Margaritiferinae J. Henderson, 1929 (1910)
- Subfamily Megalonaiadinae Heard & Guckert, 1971 accepted as Quadrulini Ihering, 1901
- Subfamily Modellnaiinae Brandt, 1974 (1)
- Subfamily Nodulariinae Starobogatov & Zatravkin, 1987 accepted as Nodulariini Starobogatov & Zatravkin, 1987
- Subfamily Parreysiinae J. Henderson, 1935 (150)
- Subfamily Physunioninae Starobogatov, 1970 accepted as Contradentini Modell, 1942
- Subfamily Pseudanodontinae Stadnichenko, 1984 accepted as Anodontini Rafinesque, 1820
- Subfamily Pseudodontinae Frierson, 1927 (60)
- Subfamily Psilunioninae Starobogatov, 1970
- Subfamily Qiyangiinae J.-H. Chen, 1983 † (66)
- Subfamily Quadrulinae Ihering, 1901 accepted as Quadrulini Ihering, 1901
- Subfamily Rectidentinae Modell, 1942 (134)
- Subfamily Strophitinae Starobogatov, 1970 accepted as Anodontini Rafinesque, 1820
- Subfamily Unionidae incertae sedis (357)
- Subfamily Unioninae Rafinesque, 1820 (790)
- Tribe Aculamprotulini X.-C. Huang & X.-P. Wu, 2019 (8)
- Tribe Anodontini Rafinesque, 1820 (104)
- Tribe Cristariini Lopes-Lima, Bogan & Froufe, 2017 (64)
- Tribe Cuneopsini Mongin, 1963 accepted as Cuneopsinae Mongin, 1963
- Tribe Lanceolariini Froufe, Lopes-Lima & Bogan, 2017 (22)
- Tribe Lepidodesmini X.-C. Huang & X.-P. Wu, 2019 (9)
- Tribe Middendorffinaiini Lopes-Lima, Bolotov & Bogan, 2020 (1)
- Tribe Nodulariini Starobogatov & Zatravkin, 1987 accepted as Oxynaiini Starobogatov, 1970
- Tribe Oxynaiini Starobogatov, 1970 (141)
- Tribe Unionini Rafinesque, 1820 (441)
- Genus Acuticosta C. T. Simpson, 1900 (23)
- Genus Alasmidens A. H. Clarke, 1981 accepted as Alasmidonta (Alasmidens) A. H. Clarke, 1981
- Genus Alasminota Ortmann, 1914 accepted as Lasmigona Rafinesque, 1831
- Genus Alasmodon G. B. Sowerby I, 1824 accepted as Alasmidonta Say, 1818
- Genus Alasmodonta [sic] accepted as Alasmidonta Say, 1818
- Genus Amblamodon Rafinesque, 1831 accepted as Amblasmodon Rafinesque, 1831
- Genus Amblasmodon Rafinesque, 1831 accepted as Lasmigona Rafinesque, 1831
- Genus Anadontoides [sic] accepted as Anodontoides C. T. Simpson, 1898
- Genus Anelasmodon Agassiz, 1846 accepted as Alasmidonta Say, 1818
- Genus Anelasmodonta Herrmannsen, 1846 accepted as Alasmidonta Say, 1818
- Genus Anodon Oken, 1815 accepted as Anodonta Lamarck, 1799
- Genus Anodontes Cuvier, 1817 accepted as Anodontites Bruguière, 1792
- Genus Anodontopsis C. T. Simpson, 1898 accepted as Anodontoides C. T. Simpson, 1898
- Genus Arkansia Ortmann & B. Walker, 1912 accepted as Arcidens C. T. Simpson, 1900
- Genus Arnoldina Hannibal, 1912 accepted as Anodonta Lamarck, 1799
- Genus Batavusiana Bourguignat, 1889 accepted as Unio (Batavusiana) Bourguignat, 1889
- Genus Betekeia Starobogatov, 1970 † (7)
- Genus Bogatschevinaia Starobogatov, 1970 † accepted as Rhombuniopsis (Bogatschevinaia) Starobogatov, 1970 †
- Genus Brachyanodon Crosse & P. Fischer, 1894 accepted as Anodonta Lamarck, 1799
- Genus Bullella C. T. Simpson, 1900 accepted as Alasmidonta Say, 1818
- Genus Cafferia C. T. Simpson, 1900 accepted as Unio Philipsson, 1788
- Genus Calceola Swainson, 1840 accepted as Alasmidonta Say, 1818
- Genus Complanaria Swainson, 1840 accepted as Lasmigona Rafinesque, 1831
- Genus Consentunio Jatsko, 1972 accepted as Unio (Crassiana) Servain, 1882
- Genus Crassiana Servain, 1882 accepted as Unio Philipsson, 1788
- Genus Crassunio Modell, 1964 accepted as Unio (Crassiana) Servain, 1882
- Genus Decurambis Rafinesque, 1831 accepted as Alasmidonta Say, 1818
- Genus Diaurora T. D. A. Cockerell, 1903 (2)
- Genus Elasmigena Agassiz, 1846 accepted as Elasmogona Agassiz, 1846
- Genus Elasmogena Agassiz, 1846 accepted as Elasmogona Agassiz, 1846
- Genus Elasmogona Agassiz, 1846 accepted as Lasmigona Rafinesque, 1831
- Genus Eolymnium Prashad, 1919 accepted as Unio Philipsson, 1788
- Genus Euphrata Pallary, 1933 accepted as Anodonta Lamarck, 1799
- Genus Flexiplis Rafinesque, 1831 accepted as Pyganodon Crosse & P. Fischer, 1894
- Genus Flexiptis Rafinesque, 1831 accepted as Pyganodon Crosse & P. Fischer, 1894
- Genus Hemiodon Swainson, 1840 accepted as Strophitus Rafinesque, 1820
- Genus Heterunio Lindholm, 1932 † (7)
- Genus Jugosus C. T. Simpson, 1914 accepted as Alasmidonta Say, 1818
- Genus Limnium accepted as Lymnium Moquin-Tandon, 1856
- Genus Lymnadea [sic] accepted as Lymnadia G. B. Sowerby II, 1839
- Genus Lymnadia G. B. Sowerby II, 1839 accepted as Potamilus Rafinesque, 1818
- Genus Lymnium Moquin-Tandon, 1856 accepted as Unio Philipsson, 1788
- Genus Margarita I. Lea, 1836
- Genus Margaron I. Lea, 1852
- Genus Mesanodon Crosse & P. Fischer, 1894 accepted as Anodonta Lamarck, 1799
- Genus Migranaja Hannibal, 1912 accepted as Potomida Swainson, 1840
- Genus Modellinaia Starobogatov, 1970 † (1)
- Genus Monodonta Say, 1817 accepted as Alasmidonta Say, 1818
- Genus Mysca W. Turton, 1822 accepted as Unio Philipsson, 1788
- Genus Nayadina De Gregorio, 1914 accepted as Utterbackia F. C. Baker, 1927
- Genus Nemrodia Pallary, 1939 accepted as Unio (Eolymnium) Prashad, 1919
- Genus Nodularidia T. D. A. Cockerell, 1901 accepted as Nodularia Conrad, 1853
- Genus Oxynaia F. Haas, 1913 accepted as Nodularia Conrad, 1853
- Genus Pagias [sic] accepted as Pegias C. T. Simpson, 1900
- Genus Palindonaia Modell, 1950 † (6)
- Genus Pictunio Jatsko, 1972 accepted as Unio Philipsson, 1788
- Genus Platynaias B. Walker, 1918 accepted as Lasmigona Rafinesque, 1831
- Genus Pressodonta C. T. Simpson, 1900 accepted as Alasmidonta Say, 1818
- Genus Pristinunio Starobogatov, 1970 † (15)
- Genus Protunio P. Haas, 1913 (1)
- Genus Pseudobaphia C. T. Simpson, 1900 (4)
- Genus Pterosygna Rafinesque, 1831 accepted as Pterosyna Rafinesque, 1831
- Genus Pterosyna Rafinesque, 1831 accepted as Lasmigona Rafinesque, 1831
- Genus Rhombunio Germain, 1911 accepted as Potomida Swainson, 1840
- Genus Rhombuniopsis F. Haas, 1920 (12)
- Genus Rombunio accepted as Rhombunio Germain, 1911
- Genus Rugifera C. T. Simpson, 1900 accepted as Alasmidonta Say, 1818
- Genus Rumanunio Starobogatov, 1970 † (4)
- Genus Schleschiella Modell, 1950 accepted as Rhipidodonta Mörch, 1853
- Genus Sculptunio Lindholm, 1932 † (1)
- Genus Sibirunio Starobogatov, 1970 † (3)
- Genus Simpsoniconcha Frierson, 1914 accepted as Simpsonaias Frierson, 1914
- Genus Sulcularia Rafinesque, 1831 accepted as Lasmigona Rafinesque, 1831
- Genus Tuberunio Lindholm, 1932 † (2)
- Genus Unio Philipsson, 1788 (353)
- Subgenus Unio (Actinonaias) Crosse & P. Fischer, 1894 accepted as Actinonaias Crosse & P. Fischer, 1894
- Subgenus Unio (Alasmodon) G. B. Sowerby I, 1824 accepted as Alasmidonta Say, 1818
- Subgenus Unio (Alasmodonta) Say, 1818 accepted as Alasmodonta [sic]
- Subgenus Unio (Amphinaias) Crosse & P. Fischer, 1894 accepted as Quadrula Rafinesque, 1820
- Subgenus Unio (Anodon) Swainson, 1840 accepted as Anodonta Lamarck, 1799
- Subgenus Unio (Anodonta) Lamarck, 1799 accepted as Anodonta Lamarck, 1799
- Subgenus Unio (Anodontes) Cuvier, 1817 accepted as Anodontites Bruguière, 1792
- Subgenus Unio (Arconaia) Conrad, 1865 accepted as Lanceolaria Conrad, 1853
- Subgenus Unio (Arotonaias) E. von Martens, 1900 accepted as Arotonaias E. von Martens, 1900
- Subgenus Unio (Aximedia) Rafinesque, 1820 accepted as Pleurobema Rafinesque, 1819
- Subgenus Unio (Baphia) Gray, 1847 accepted as Vulsella Röding, 1798
- Subgenus Unio (Bariosta) Rafinesque, 1831 accepted as Plectomerus Conrad, 1853
- Subgenus Unio (Baryana) Locard, 1889 accepted as Pseudunio F. Haas, 1910
- Subgenus Unio (Barynaias) Fischer & Crosse, 1894 accepted as Barynaias Crosse & P. Fischer, 1894
- Subgenus Unio (Bataviana) Servain, 1882 accepted as Unio (Crassiana) Servain, 1882
- Subgenus Unio (Batavusiana) Bourguignat, 1889 accepted as Unio (Crassiana) Servain, 1882
- Subgenus Unio (Cafferia) C. T. Simpson, 1900 accepted as Cafferia C. T. Simpson, 1900
- Subgenus Unio (Canthyria) Swainson, 1840 accepted as Elliptio Rafinesque, 1819
- Subgenus Unio (Coelatura) Conrad, 1853 accepted as Coelatura Conrad, 1853
- Subgenus Unio (Consentunio) Jatsko, 1972 accepted as Unio (Crassiana) Servain, 1882
- Subgenus Unio (Crassiana) Servain, 1882 accepted as Unio Philipsson, 1788
- Subgenus Unio (Crassunio) Modell, 1964 accepted as Unio (Crassiana) Servain, 1882
- Subgenus Unio (Cuneopsis) C. T. Simpson, 1900 accepted as Cuneopsis C. T. Simpson, 1900
- Subgenus Unio (Cyrtonaias) Crosse & P. Fischer, 1894 accepted as Cyrtonaias Crosse & P. Fischer, 1894
- Subgenus Unio (Delphinonaias) Crosse & P. Fischer, 1894 accepted as Delphinonaias Crosse & P. Fischer, 1894
- Subgenus Unio (Diplodon) Spix, 1827 accepted as Diplodon Spix, 1827
- Subgenus Unio (Disconaias) Crosse & P. Fischer, 1894 accepted as Disconaias Crosse & P. Fischer, 1894
- Subgenus Unio (Dysnomia) Agassiz, 1852
- Subgenus Unio (Elliptio) Rafinesque, 1819 accepted as Elliptio Rafinesque, 1819
- Subgenus Unio (Eolymnium) Prashad, 1919 accepted as Unio Philipsson, 1788
- Subgenus Unio (Eurynia) Rafinesque, 1819 accepted as Eurynia Rafinesque, 1819
- Subgenus Unio (Glebula) Conrad, 1853 accepted as Glebula Conrad, 1853
- Subgenus Unio (Grandidieria) Bourguignat, 1885 accepted as Grandidieria Bourguignat, 1885
- Subgenus Unio (Heterunio) Lindholm, 1932 † accepted as Heterunio Lindholm, 1932 †
- Species Unio (Heterunio) exquisitus Lindholm, 1932 † accepted as Heterunio exquisitus (Lindholm, 1932) †
- Subgenus Unio (Iridea) Swainson, 1840 accepted as Diplodon Spix, 1827
- Subgenus Unio (Lampsilis) Rafinesque, 1820 accepted as Lampsilis Rafinesque, 1820
- Subgenus Unio (Lanceolaria) Conrad, 1853 accepted as Lanceolaria Conrad, 1853
- Subgenus Unio (Lemiox) Rafinesque, 1831 accepted as Lemiox Rafinesque, 1831
- Subgenus Unio (Leptodea) Rafinesque, 1820 accepted as Leptodea Rafinesque, 1820
- Subgenus Unio (Ligumia) Swainson, 1840 accepted as Ligumia Swainson, 1840
- Subgenus Unio (Limnium) [sic] accepted as Unio Philipsson, 1788
- Subgenus Unio (Limnoscapha) Lindholm, 1932 † accepted as Limnoscapha Lindholm, 1932 †
- Subgenus Unio (Loxopleurus) Meek, 1871 † accepted as Protamblema Modell, 1957 †
- Subgenus Unio (Lymnium) Moquin-Tandon, 1856 accepted as Unio Philipsson, 1788
- Subgenus Unio (Megadomus) Swainson, 1840 accepted as Lasmigona Rafinesque, 1831
- Subgenus Unio (Metaptera) Rafinesque, 1820 accepted as Potamilus Rafinesque, 1818
- Subgenus Unio (Microdontia) Tapparone Canefri, 1883 accepted as Microdontia Tapparone Canefri, 1883
- Subgenus Unio (Micronaias) C. T. Simpson, 1900 accepted as Micronaias C. T. Simpson, 1900
- Subgenus Unio (Monocondylaea) A. d'Orbigny, 1835 accepted as Monocondylaea A. d'Orbigny, 1835
- Subgenus Unio (Nemrodia) Pallary, 1939 accepted as Nemrodia Pallary, 1939
- Subgenus Unio (Nephronaias) Crosse & P. Fischer, 1894 accepted as Nephronaias Crosse & P. Fischer, 1894
- Subgenus Unio (Niaea) F. Sandberger, 1875 †
- Subgenus Unio (Nippononaia) K. Suzuki, 1941 † accepted as Nippononaia K. Suzuki, 1941 †
- Subgenus Unio (Nodularia) Conrad, 1853 accepted as Nodularia Conrad, 1853
- Subgenus Unio (Obovaria) Rafinesque, 1819 accepted as Obovaria Rafinesque, 1819
- Subgenus Unio (Pachynaias) Crosse & P. Fischer, 1894 accepted as Pachynaias Crosse & P. Fischer, 1894
- Subgenus Unio (Palaeunio) Q.-H. Ma, 1999 † accepted as Eocuneopsis F.-X. Guo, 1988 †
- Subgenus Unio (Parreysia) Conrad, 1853 accepted as Parreysia Conrad, 1853
- Subgenus Unio (Pleurobema) Rafinesque, 1819 accepted as Pleurobema Rafinesque, 1819
- Subgenus Unio (Pseudosturia) Chepalyga, 1965 † accepted as Pseudosturia Chepalyga, 1965 †
- Subgenus Unio (Psilunio) Stefanescu, 1896 † accepted as Psilunio Stefanescu, 1896 †
- Subgenus Unio (Psoronaias) Crosse & P. Fischer, 1894 accepted as Psoronaias Crosse & P. Fischer, 1894
- Subgenus Unio (Quadrula) Rafinesque, 1820 accepted as Quadrula Rafinesque, 1820
- Subgenus Unio (Rhipidodonta) Mörch, 1853 accepted as Rhipidodonta Mörch, 1853
- Subgenus Unio (Rotundaria) Rafinesque, 1820 accepted as Obovaria Rafinesque, 1819
- Subgenus Unio (Rumanunio) Starobogatov, 1970 † accepted as Rumanunio Starobogatov, 1970 †
- Subgenus Unio (Rytia) Stefanescu, 1896 † accepted as Potomida Swainson, 1840
- Subgenus Unio (Sayunio) De Gregorio, 1914 accepted as Hemistena Rafinesque, 1820
- Subgenus Unio (Sculptunio) Lindholm, 1932 † accepted as Sculptunio Lindholm, 1932 †
- Subgenus Unio (Simonaias) Crosse & P. Fischer, 1894 accepted as Nephronaias Crosse & P. Fischer, 1894
- Subgenus Unio (Sphenonaias) Crosse & P. Fischer, 1894 accepted as Sphenonaias Crosse & P. Fischer, 1894
- Subgenus Unio (Subreniformiana) Fagot, 1893
- Subgenus Unio (Symphynota) I. Lea, 1829 accepted as Potamilus Rafinesque, 1818
- Subgenus Unio (Theliderma) Swainson, 1840 accepted as Theliderma Swainson, 1840
- Subgenus Unio (Toxolasma) Rafinesque, 1831 accepted as Toxolasma Rafinesque, 1831
- Subgenus Unio (Truncilla) Rafinesque, 1819 accepted as Truncilla Rafinesque, 1819
- Subgenus Unio (Tuberunio) Lindholm, 1932 † accepted as Tuberunio Lindholm, 1932 †
- Subgenus Unio (Tumidunio) Jatsko, 1972 accepted as Unio Philipsson, 1788
- Subgenus Unio (Tumidusiana) Locard, 1889 accepted as Unio Philipsson, 1788
- Subgenus Unio (Unio) Philipsson, 1788 accepted as Unio Philipsson, 1788
- Subgenus Unio (Uniomerus) Conrad, 1853 accepted as Uniomerus Conrad, 1853
- Subgenus Unio (Wenziella) Modell, 1958 † accepted as Potomida Swainson, 1840
- Species Unio abacoides Haldeman, 1846 accepted as Dromus dromas (I. Lea, 1834)
- Species Unio abacus Haldeman, 1842 accepted as Ptychobranchus fasciolaris (Rafinesque, 1820)
- Species Unio abbevillensis I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio abbreviatus Westerlund, 1897 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio abbreviatus Goldfuss, 1837 †
- Species Unio aberrans I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio aberti Conrad, 1850 accepted as Cyprogenia aberti (Conrad, 1850)
- Species Unio ablatus I. Lea, 1863 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio abnormis Morelet, 1863 accepted as Physunio superbus (I. Lea, 1843)
- Species Unio abruptus Say, 1831 accepted as Lampsilis abrupta (Say, 1831)
- Species Unio abrus Kobelt, 1913 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio abyssinicus E. von Martens, 1866
- Species Unio accultus [sic] accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio acrorrhynchus E. von Martens, 1894 accepted as Lanceolaria acrorrhyncha (E. von Martens, 1894)
- Species Unio acuens I. Lea, 1871 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio acuminatus H. Adams, 1866 accepted as Nitia acuminata (H. Adams, 1866)
- Species Unio acuticarinatus Pavlović, 1931 †
- Species Unio acutirostris I. Lea, 1866 accepted as Diplodon parallelopipedon (I. Lea, 1834)
- Species Unio acutissimus I. Lea, 1831 accepted as Medionidus acutissimus (I. Lea, 1831)
- Species Unio acutus Cobălcescu, 1883 † accepted as Jazkoa sturzae (Cobălcescu, 1883) †
- Species Unio acutus J. Sowerby, 1813 † accepted as Carbonicola acuta (J. Sowerby, 1813) †
- Species Unio adensis Atanacković, 1959 †
- Species Unio adonus Locard, 1889 accepted as Unio batavus Nilsson, 1822
- Species Unio aduncus J. De C. Sowerby, 1828 †
- Species Unio aegyptiacus Cailliaud, 1823 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio aeneus Jickeli, 1874 accepted as Unio dembeae Reeve, 1865
- Species Unio aequatorius Morelet, 1885 accepted as Coelatura gabonensis (Küster, 1862)
- Species Unio aequatus I. Lea, 1857 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio aeruginosus Morelet, 1849 accepted as Nephronaias aeruginosa (Morelet, 1849)
- Species Unio aesopiformis Whitfield, 1903 † accepted as Plethobasus aesopiformis (Whitfield, 1903) †
- Species Unio aesopus Green, 1827 accepted as Plethobasus cyphyus (Rafinesque, 1820)
- Species Unio aethiops I. Lea, 1860 accepted as Diplodon aethiops (I. Lea, 1860)
- Species Unio aferula I. Lea, 1864 accepted as Nyassunio nyassaensis (I. Lea, 1864)
- Species Unio affinis I. Lea, 1852 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio affinis Heude, 1875 accepted as Unio polystictus Heude, 1877
- Species Unio affuvelensis "Matheron" †
- Species Unio africanus I. Lea, 1856 accepted as Unio caffer Krauss, 1848
- Species Unio agrestis (T. Brown, 1843) † accepted as Carbonicola acuta (J. Sowerby, 1813) †
- Species Unio aheneus I. Lea, 1843 accepted as Elliptio ahenea (I. Lea, 1843)
- Species Unio ailikehuensis J.-M. Wei, 1984 † accepted as Unio grabaui Martinson, 1956 †
- Species Unio alabamensis Conrad, 1834 accepted as Potamilus inflatus (I. Lea, 1831)
- Species Unio alatoides I. Lea, 1868 † accepted as Potamilus alatus (Say, 1817)
- Species Unio alatus Say, 1817 accepted as Potamilus alatus (Say, 1817)
- Species Unio albertensis Whiteaves, 1885 † accepted as Elliptio albertensis (Whiteaves, 1885) †
- Species Unio alcobacensis Choffat, 1885 † accepted as Lamellidens alcobacensis (Choffat, 1885) †
- Species Unio aldamii (T. Brown, 1843) † accepted as Carbonicola aldamii (T. Brown, 1843) †
- Species Unio aldrichi C. A. White, 1878 † accepted as Rhabdotophorus aldrichi (C. A. White, 1878) †
- Species Unio alexandri Kobelt & Rolle, 1895 accepted as Unio delicatus I. Lea, 1863
- Species Unio alexeevi Mangikian, 1929 † accepted as Unio (Unio) pictorum alexeevi Mangikian, 1929 †
- Species Unio alexejevi [sic] † accepted as Unio (Unio) pictorum alexeevi Mangikian, 1929 †
- Species Unio alfierianus Bourguignat, 1885 accepted as Unio dembeae Reeve, 1865
- Species Unio alienigenus Crosse & P. Fischer, 1893 accepted as Cyrtonaias umbrosa (I. Lea, 1856)
- Species Unio alixus Dall, 1913 † accepted as Pleurobema alixus (Dall, 1913) †
- Species Unio alpina Matheron, 1843 †
- Species Unio altecarinatus Penecke, 1883 † accepted as Psilunio altecarinatus (Penecke, 1883) †
- Species Unio altilis Conrad, 1834 accepted as Hamiota altilis (Conrad, 1834)
- Species Unio altus Conrad, 1854 accepted as Pleurobema altum (Conrad, 1854)
- Species Unio amabilis I. Lea, 1865 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio amarillensis Stanton, 1916 † accepted as Fusconaia amarillensis (Stanton, 1916) †
- Species Unio amazonensis I. Lea, 1860 accepted as Anodontites trigonus (Spix, 1827)
- Species Unio ambifarius E. von Martens, 1897 accepted as Coelatura ratidota (Charmes, 1885)
- Species Unio ambiguus R. A. Philippi, 1847 accepted as Velesunio ambiguus (R. A. Philippi, 1847)
- Species Unio amitinus Bogachev † accepted as Jazkoa sturzae (Cobălcescu, 1883) †
- Species Unio amnicus Rossmässler, 1835 accepted as Unio nanus Lamarck, 1819
- Species Unio amoenus I. Lea, 1840 accepted as Villosa iris (I. Lea, 1829)
- Species Unio amoenus X.-Z. Liu, 1988 †
- Species Unio amplus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio ampullaceus I. Lea, 1866 accepted as Diplodon uruguayensis (I. Lea, 1860)
- Species Unio amygdalum I. Lea, 1843 accepted as Villosa amygdalum (I. Lea, 1843)
- Species Unio anaticulus I. Lea, 1861 accepted as Pleurobema decisum (I. Lea, 1831)
- Species Unio anceps Deshayes, 1876 accepted as Scabies anceps (Deshayes, 1876)
- Species Unio anceyi Kobelt, 1912 accepted as Unio delicatus I. Lea, 1863
- Species Unio ancyrensis Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio andersonensis I. Lea, 1872 accepted as Fusconaia cor (Conrad, 1834)
- Species Unio andersoni J. Hudson, 1963 †
- Species Unio andersoniana G. Nevill, 1877 accepted as Indonaia andersoniana (G. Nevill, 1877)
- Species Unio andrussovi "G. I. Popov, 1965" † accepted as Betekeia andrussovi "(G. I. Popov, 1965)" †
- Species Unio anemprosthus Locard, 1883 accepted as Unio delicatus I. Lea, 1863
- Species Unio anfractidens Jatsko, 1972 †
- Species Unio angarensis (Popova, 1981) †
- Species Unio angasi G. B. Sowerby II, 1867 accepted as Velesunio angasi (G. B. Sowerby II, 1867)
- Species Unio angoniensis Preston, 1910 accepted as Coelatura hypsiprymna (E. von Martens, 1897)
- Species Unio angustatus I. Lea, 1831 accepted as Elliptio angustata (I. Lea, 1831)
- Species Unio annulatus Kobelt, 1911 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio anodontoides I. Lea, 1831 accepted as Lampsilis teres (Rafinesque, 1820)
- Species Unio anodontoides Noulet, 1846 † accepted as Hyriopsis hannae Modell, 1941 †
- Species Unio ansaiensis J.-S. Yu & R.-J. Zhang, 1980 †
- Species Unio ansticei J. De C. Sowerby, 1840 † accepted as Gilbertsonia ansticei (J. De C. Sowerby, 1840) †
- Species Unio anthonyi I. Lea, 1861 accepted as Elliptio monroensis (I. Lea, 1843)
- Species Unio antiochianus Locard, 1883 accepted as Unio delicatus I. Lea, 1863
- Species Unio antiqua (T. Kobayashi & K. Suzuki, 1937) † accepted as Unio antiquus (T. Kobayashi & K. Suzuki, 1937) †
- Species Unio antiquatus Anton, 1839
- Species Unio antiquus J. De C. Sowerby, 1828 †
- Species Unio antiquus (T. Kobayashi & K. Suzuki, 1937) †
- Species Unio apicinus I. Lea, 1857 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio apiculatus Say, 1829 accepted as Quadrula apiculata (Say, 1829)
- Species Unio appressus I. Lea, 1871 accepted as Fusconaia cuneolus (I. Lea, 1840)
- Species Unio apprimus I. Lea, 1866 accepted as Diplodon uruguayensis (I. Lea, 1860)
- Species Unio approximus I. Lea, 1845 accepted as Lampsilis hydiana (I. Lea, 1838)
- Species Unio apscheronicus K. A. Ali-Zade, 1939 †
- Species Unio aquilinus J. De C. Sowerby, 1840 † accepted as Carbonicola aquilina (J. De C. Sowerby, 1840) †
- Species Unio aquilus I. Lea, 1857 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio aradae R. A. Philippi, 1844 accepted as Unio mancus turtonii Payraudeau, 1826
- Species Unio aragangensis C. M. Kolesnikov, 1956 †
- Species Unio aratus Conrad, 1849 accepted as Unio plectophorus Conrad, 1849
- Species Unio aratus I. Lea, 1843 accepted as Micronaias arata (I. Lea, 1843)
- Species Unio araucanus R. A. Philippi, 1847 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio araxenus Drouët, 1881 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio arcaeformis I. Lea, 1831 accepted as Epioblasma arcaeformis (I. Lea, 1831)
- Species Unio arciruga Teisseyre, 1911 †
- Species Unio arctatus Conrad, 1834 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio arctior I. Lea, 1838 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio arcus Conrad, 1834 accepted as Elliptio arca (Conrad, 1834)
- Species Unio argenteus I. Lea, 1841 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio argetoianui Ionescu-Argetoaia, 1918 †
- Species Unio arizonensis J. Henderson, 1934 † accepted as Plesielliptio arizonensis (J. Henderson, 1934) †
- Species Unio arkansasensis I. Lea, 1862 accepted as Obovaria arkansasensis (I. Lea, 1862)
- Species Unio arkitica Repman, 1963 †
- Species Unio armeniacus Kobelt, 1911 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio arquatus Conrad, 1854 accepted as Ligumia recta (Lamarck, 1819)
- Species Unio ascanius Kobelt, 1912 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio ascia Hanley, 1856 accepted as Lens contradens (I. Lea, 1838)
- Species Unio askewi W. A. Marsh, 1896 accepted as Fusconaia askewi (W. A. Marsh, 1896)
- Species Unio asper I. Lea, 1831 accepted as Quadrula apiculata (Say, 1829)
- Species Unio asperatus I. Lea, 1861 accepted as Rotundaria asperata (I. Lea, 1861)
- Species Unio asperrimus I. Lea, 1831 accepted as Quadrula quadrula (Rafinesque, 1820)
- Species Unio asperulus I. Lea, 1866 accepted as Lens contradens (I. Lea, 1838)
- Species Unio asturianus Delvene, Munt, Piñuela & García-Ramos, 2016 †
- Species Unio atavus M. Hörnes, 1864 †
- Species Unio ater I. Lea, 1829 accepted as Potamilus purpuratus (Lamarck, 1819)
- Species Unio ater Nilsson, 1823 accepted as Unio crassus Philipsson, 1788
- Species Unio athanasii Ionescu-Argetoaia, 1918 †
- Species Unio athesinus Adami, 1886 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio athleta Lindholm, 1932 † accepted as Betekeia athleta (Lindholm, 1932) †
- Species Unio atrata Swainson, 1823 accepted as Leptodea fragilis (Rafinesque, 1820)
- Species Unio atratus [sic] † accepted as Unio utratus Goldfuss, 1837 †
- Species Unio atrocostatus I. Lea, 1845 accepted as Amblema plicata (Say, 1817)
- Species Unio atromarginatus I. Lea, 1840 accepted as Elliptoideus sloatianus (I. Lea, 1840)
- Species Unio attenuatus I. Lea, 1872 accepted as Elliptio folliculata (I. Lea, 1838)
- Species Unio attiai L. R. Cox, 1955 † accepted as Pleiodon attiai (L. R. Cox, 1955) †
- Species Unio atticus Gaudry & P. Fischer, 1867 † accepted as Potomida attica (Gaudry & P. Fischer, 1867) †
- Species Unio aucklandicus J. E. Gray, 1843 accepted as Echyridella aucklandica (J. E. Gray, 1843)
- Species Unio aureus I. Lea, 1859 accepted as Rotundaria aurea (I. Lea, 1859)
- Species Unio auricularius Spengler, 1793 accepted as Pseudunio auricularius (Spengler, 1793)
- Species Unio auroreus Heude, 1883 accepted as Diaurora aurorea (Heude, 1883)
- Species Unio austenii Forbes, 1856 †
- Species Unio australis Lamarck, 1819 accepted as Hyridella australis (Lamarck, 1819)
- Species Unio avangardensis Yakushina, 1964 †
- Species Unio averellii B. H. Wright, 1888 accepted as Villosa vibex (Conrad, 1834)
- Species Unio averyi I. Lea, 1859 accepted as Barynaias caldwellii (I. Lea, 1858)
- Species Unio axiacus Locard, 1883 accepted as Unio delicatus I. Lea, 1863
- Species Unio aztecorum R. A. Philippi, 1847 accepted as Nephronaias aztecorum (R. A. Philippi, 1847)
- Species Unio babensis Kobelt, 1913 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio babori (Petrbok, 1912) †
- Species Unio bachtynicus Gozhik & Prisyazhnyuk, 1971 †
- Species Unio baeticus Kobelt, 1888 accepted as Unio tumidiformis Castro, 1885
- Species Unio baeuerleini Modell, 1931 †
- Species Unio bagdadensis Bourguignat, 1852 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio baicalensis Rammelmeyer, 1940 † accepted as Baicalinaia baicalensis (Rammelmeyer, 1940) †
- Species Unio baileyi Logan, 1900 †
- Species Unio bainzurchensis Martinson & Hong, 1961 †
- Species Unio bairdianus I. Lea, 1857 accepted as Toxolasma texasiense (I. Lea, 1857)
- Species Unio bakeri H. Adams, 1866 accepted as Coelatura bakeri (H. Adams, 1866)
- Species Unio bakoyi Rochebrune, 1882 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio balbinensis Ragozin, 1954 †
- Species Unio baldwinensis I. Lea, 1859 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio balonnensis Conrad, 1850 accepted as Velesunio ambiguus (R. A. Philippi, 1847)
- Species Unio baltae Teisseyre, 1911 †
- Species Unio baltavarensis Halaváts, 1923 † accepted as Psilunio jurisici (Brusina, 1896) †
- Species Unio banae Botez, 1914 †
- Species Unio baotashanensis Q.-H. Ma, 1984 † accepted as Solenoides tanggulaensis (S.-X. Wen, 1979) †
- Species Unio barabanovskiensis Lebedev, 1958 † accepted as Itatia barabanovskiensis (Lebedev, 1958) †
- Species Unio barabanowskiensis [sic] † accepted as Unio barabanovskiensis Lebedev, 1958 †
- Species Unio barbouri C. A. White, 1895 † accepted as Ligumia barbouri (C. A. White, 1895) †
- Species Unio barnesianus I. Lea, 1838 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio barrandei Neumayr, 1875 † accepted as Psilunio sandbergeri (Neumayr, 1875) †
- Species Unio barrattii I. Lea, 1852 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio barraudi Bonhomme, 1840 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio barrotti Küster, 1861 accepted as Elliptio producta (Conrad, 1836)
- Species Unio barzaviae Jekelius, 1932 †
- Species Unio basalis I. Lea, 1872 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio batavellus Locard, 1885 accepted as Unio crassus Philipsson, 1788
- Species Unio batavus Nilsson, 1822 accepted as Unio crassus Philipsson, 1788
- Species Unio batilliformis Ludwig, 1861 †
- Species Unio baudoni de Folin & Bérillon, 1874
- Species Unio baueri Stanton, 1916 †
- Species Unio bazini Heude, 1877 accepted as Lamprotula bazini (Heude, 1877)
- Species Unio beadleianus I. Lea, 1861 accepted as Pleurobema beadleianum (I. Lea, 1861)
- Species Unio bealei I. Lea, 1862 accepted as Toxolasma texasiense (I. Lea, 1857)
- Species Unio beaverensis I. Lea, 1868 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio bednalli Tate, 1882 accepted as Velesunio angasi (G. B. Sowerby II, 1867)
- Species Unio belliplicatus Meek, 1871 † accepted as Protamblema belliplicata (Meek, 1871) †
- Species Unio bellulus I. Lea, 1872 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio benacinus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio bengalensis I. Lea, 1838 accepted as Simpsonella purpurea (Valenciennes, 1827)
- Species Unio berlandieri I. Lea, 1857 accepted as Unio berlandierii I. Lea, 1857
- Species Unio berlandierii I. Lea, 1857 accepted as Cyrtonaias tampicoensis (I. Lea, 1838)
- Species Unio beroeus Kobelt, 1913 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio bersenevi Popova, 1963 † accepted as Nodularia bersenevi (Popova, 1963) †
- Species Unio berytensis Kobelt & Rolle, 1895 accepted as Unio delicatus I. Lea, 1863
- Species Unio besckeanus Dunker, 1849 accepted as Diplodon ellipticus Spix, 1827
- Species Unio bessarabiensis Pavlov, 1925 †
- Species Unio betekeiensis Lindholm, 1932 † accepted as Sibirunio betekeiensis (Lindholm, 1932) †
- Species Unio beyrichi Neumayr, 1875 † accepted as Cuneopsidea beyrichi (Neumayr, 1875) †
- Species Unio bhamoensis Theobald, 1873 accepted as Leoparreysia tavoyensis (A. Gould, 1843)
- Species Unio biangularis I. Lea, 1840 accepted as Ortmanniana pectorosa (Conrad, 1834)
- Species Unio biangulatus "I. Lea, 1842" accepted as Unio biangularis I. Lea, 1840
- Species Unio biarmicus Bogachev, 1961 †
- Species Unio bicaelatus Reeve, 1865 accepted as Leaunio lienosus lienosus (Conrad, 1834)
- Species Unio bielzi Czekelius, 1864 † accepted as Potomida bielzi (Czekelius, 1864) †
- Species Unio bielzii T. Fuchs, 1870 † accepted as Unio mihanovici Brusina, 1896 †
- Species Unio biemarginatus I. Lea, 1857 accepted as Epioblasma biemarginata (I. Lea, 1857)
- Species Unio biesianus Heude, 1877 accepted as Pseudobaphia biesiana (Heude, 1877)
- Species Unio biesopoides Whitfield, 1907 † accepted as Plethobasus biesopoides (Whitfield, 1907) †
- Species Unio bigbyensis I. Lea, 1841 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio billottianus Charmes, 1885 accepted as Coelatura ratidota (Charmes, 1885)
- Species Unio binneyi I. Lea, 1845 accepted as Diplodon rhuacoicus (A. d'Orbigny, 1835)
- Species Unio biornatus L. S. Russell, 1932 † accepted as Protelliptio biornatus (L. S. Russell, 1932) †
- Species Unio bipennis (T. Brown, 1843) † accepted as Carbonicola bipennis (T. Brown, 1843) †
- Species Unio biplicatus Bielz, 1864 † accepted as Psilunio biplicatus (Bielz, 1864) †
- Species Unio bisselianus I. Lea, 1867 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio bithynicus Kobelt, 1893 accepted as Elongaria orientalis (I. Lea, 1840)
- Species Unio bitlisensis Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio bittneri Penecke, 1883 † accepted as Unio hoernesi Penecke, 1883 †
- Species Unio bituberculosus E. von Martens, 1874 † accepted as Sculptunio bituberculosus (E. von Martens, 1874) †
- Species Unio bitumen C. W. Cooke, 1919 † accepted as Pseudophopsis bitumen (C. W. Cooke, 1919) †
- Species Unio biveri Fabre-Taxy, 1951 †
- Species Unio biwae Kobelt, 1879 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio blanchianus Kobelt, 1913 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio blandianus I. Lea, 1857 accepted as Quadrula rumphiana (I. Lea, 1852)
- Species Unio blandingianus I. Lea, 1834 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio blumrichi Modell, 1940 †
- Species Unio boehmi E. von Martens, 1897 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio bogatschevi Grigorovich-Beresovskiy, 1915 † accepted as Potomida bogatschevi (Grigorovich-Beresovskiy, 1915) †
- Species Unio bogdanovkaensis (Gozhik, 1978) †
- Species Unio bohemicus Petrbok, 1927 †
- Species Unio bollii Call, 1881 accepted as Rotundaria petrina (A. Gould, 1855)
- Species Unio bonneaudii Eydoux, 1838 accepted as Indonaia bonneaudii (Eydoux, 1838)
- Species Unio borealis A. F. Gray, 1882 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio borellii Ancey, 1894 accepted as Coelatura mossambicensis (E. von Martens, 1860)
- Species Unio borneeensis Issel, 1874 accepted as Ctenodesma borneensis (Issel, 1874)
- Species Unio boskovici Pavlović, 1931 †
- Species Unio bosnensis Möllendorff, 1873 accepted as Unio crassus Philipsson, 1788
- Species Unio bosqui [sic] † accepted as Unio bosquianus Matheron, 1843 †
- Species Unio bosquiana Matheron, 1843 † accepted as Unio bosquianus Matheron, 1843 †
- Species Unio bosquianus Matheron, 1843 †
- Species Unio bouei Pavlović, 1931 †
- Species Unio bourguignati Landrin, 1865
- Species Unio bourguignatianus Adami, 1886 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio bourguignatianus I. Lea, 1863 accepted as Unio tigridis Bourguignat, 1852
- Species Unio bournianus I. Lea, 1840 accepted as Pleurobema clava (Lamarck, 1819)
- Species Unio boydianus I. Lea, 1840 accepted as Leptodea ochracea (Say, 1817)
- Species Unio boykinianus I. Lea, 1840 accepted as Megalonaias nervosa (Rafinesque, 1820)
- Species Unio bozdagiensis K. A. Ali-Zade, 1939 †
- Species Unio brachyopisthus C. A. White, 1876 † accepted as Plesielliptio brachyopisthus (C. A. White, 1876) †
- Species Unio brachyrhynchus Drouët, 1881 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio bracteatus A. Gould, 1855 accepted as Lampsilis bracteata (A. Gould, 1855)
- Species Unio brandisi Kobelt, 1910 accepted as Unio crassus Philipsson, 1788
- Species Unio brandtii Kobelt, 1879 accepted as Inversidens brandtii (Kobelt, 1879)
- Species Unio branimiri Brusina, 1902 † accepted as Unio haeckeli Penecke, 1883 †
- Species Unio brazosensis I. Lea, 1868 accepted as Amblema plicata (Say, 1817)
- Species Unio breviculus Call, 1887 accepted as Lampsilis reeveiana (I. Lea, 1852)
- Species Unio brevidens I. Lea, 1831 accepted as Epioblasma brevidens (I. Lea, 1831)
- Species Unio breviplicatus Noulet, 1864 † accepted as Margaritifera (Pseudunio) flabellata (Goldfuss, 1837) †
- Species Unio brevirostris Küster, 1854 accepted as Unio crassus Philipsson, 1788
- Species Unio brevis I. Lea, 1872 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio brianteus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio briarti Dautzenberg, 1901 accepted as Coelatura briarti (Dautzenberg, 1901)
- Species Unio bridouxi Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio brightoni F. R. Woodward, 1965 †
- Species Unio brimhallensis Stanton, 1916 † accepted as Lampsilis brimhallensis (Stanton, 1916) †
- Species Unio brimleyi S. H. Wright, 1897 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio brinoniensis Fabre-Taxy, 1951 †
- Species Unio broilii Modell, 1941 †
- Species Unio broti Deshayes, 1876 accepted as Unionetta fabagina (Deshayes, 1876)
- Species Unio broti Locard, 1893 † accepted as Ptychorhynchoideus broti (Locard, 1893) †
- Species Unio browni Whitfield, 1903 † accepted as Proparreysia barnumi (Pilsbry, 1904) †
- Species Unio brownianus I. Lea, 1838 accepted as Prisodon syrmatophorus (Gmelin, 1791)
- Species Unio brownii I. Lea, 1856 accepted as Diplodon delodonta (Lamarck, 1819)
- Species Unio bruguierianus Bourguignat, 1853
- Species Unio brumbyanus "I. Lea, 1842" accepted as Unio brumleyanus I. Lea, 1841
- Species Unio brumleyanus I. Lea, 1841 accepted as Ptychobranchus greenii (Conrad, 1834)
- Species Unio brunnea Bonhomme, 1840 accepted as Margaritifera (Margaritifera) margaritifera (Linnaeus, 1758)
- Species Unio brusinai Penecke, 1883 † accepted as Unio nicolaianus Brusina, 1874 †
- Species Unio brusinaiformis Modell, 1950 † accepted as Pseudosturia brusinaiformis (Modell, 1950) †
- Species Unio buarcosensis Choffat, 1885 †
- Species Unio buckleyi I. Lea, 1843 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio buddianus I. Lea, 1843 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio bugasicus Bogachev, 1961 † accepted as Bogatschevia tamanensis (Bogachev, 1961) †
- Species Unio bugensis (Gozhik, 1978) †
- Species Unio bulbosus I. Lea, 1857 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio bulloides I. Lea, 1859 accepted as Rhipidodonta variabilis (Maton, 1811)
- Species Unio burattii Brusina, 1902 † accepted as Potomida vukasoviciana (Brusina, 1874) †
- Species Unio burckhardti Mayer-Eymar, 1900 † accepted as Diplodon burckhardti (Mayer-Eymar, 1900) †
- Species Unio burgersteini Pavlović, 1931 †
- Species Unio burjatica C. M. Kolesnikov, 1956 † accepted as Unio burjaticus C. M. Kolesnikov, 1956 †
- Species Unio burjaticus C. M. Kolesnikov, 1956 †
- Species Unio burkensis I. Lea, 1859 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio burmanus Blanford, 1869 accepted as Leoparreysia burmana (Blanford, 1869)
- Species Unio burroughianus I. Lea, 1834 accepted as Rhipidodonta burroughiana (I. Lea, 1834)
- Species Unio bursapastoris B. H. Wright, 1896 accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio burtchianus S. H. Wright, 1897 accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio burtoni S. P. Woodward, 1859 accepted as Grandidieria burtoni (S. P. Woodward, 1859)
- Species Unio buxeus I. Lea, 1852 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio buxtoni B. H. Wright, 1897 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio byzantinus Drouët, 1879 accepted as Unio crassus Philipsson, 1788
- Species Unio cabeolensis Fontannes, 1880 †
- Species Unio cacao I. Lea, 1859 accepted as Rotundaria succissa (I. Lea, 1852)
- Species Unio cachetinus Bogachev, 1936 †
- Species Unio caelatus Conrad, 1834 accepted as Lemiox rimosus (Rafinesque, 1831)
- Species Unio caeruleus I. Lea, 1831 accepted as Indonaia caerulea (I. Lea, 1831)
- Species Unio caffer Krauss, 1848
- Species Unio cahabensis I. Lea, 1871 accepted as Rotundaria asperata (I. Lea, 1861)
- Species Unio cainarensis Jatsko, 1955 †
- Species Unio caipira Ihering, 1893 accepted as Diplodon caipira (Ihering, 1893)
- Species Unio calamitarum Morelet, 1849 accepted as Nephronaias calamitarum (Morelet, 1849)
- Species Unio calathus Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio calceolus I. Lea, 1827 accepted as Alasmidonta viridis (Rafinesque, 1820)
- Species Unio calderoni Kobelt, 1888 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio caldwellii I. Lea, 1858 accepted as Barynaias caldwellii (I. Lea, 1858)
- Species Unio caliginosus I. Lea, 1845 accepted as Leaunio lienosus caliginosus (I. Lea, 1845)
- Species Unio calliopsis Kobelt, 1912 accepted as Unio tigridis Bourguignat, 1852
- Species Unio callosus I. Lea, 1841 accepted as Sphenonaias callosa (I. Lea, 1841)
- Species Unio caloosaensis Dall, 1898 †
- Species Unio cambodiensis I. Lea, 1856 accepted as Lens contradens (I. Lea, 1838)
- Species Unio cambojensis G. B. Sowerby II, 1866 accepted as Lens micropterus (Morelet, 1866)
- Species Unio camelopardilis I. Lea, 1860 accepted as Villosa taeniata (Conrad, 1834)
- Species Unio camelus I. Lea, 1834 accepted as Ptychobranchus fasciolaris (Rafinesque, 1820)
- Species Unio camptodon Say, 1832 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio canadensis I. Lea, 1857 accepted as Lampsilis cardium Rafinesque, 1820
- Species Unio candaharicus T. Hutton, 1849 accepted as Lamellidens candaharicus (T. Hutton, 1849)
- Species Unio cantianus Kennard & B. B. Woodward, 1924 † accepted as Unio crassus batavus Nilsson, 1822
- Species Unio capax Green, 1832 accepted as Potamilus capax (Green, 1832)
- Species Unio capellinii Fontannes, 1880 † accepted as Potomida capellinii (Fontannes, 1880) †
- Species Unio caperatus I. Lea, 1845 accepted as Dromus dromas (I. Lea, 1834)
- Species Unio capillaris I. Lea, 1834 accepted as Epioblasma personata (Say, 1829)
- Species Unio capillus Say, 1831 accepted as Paetulunio fabalis (I. Lea, 1831)
- Species Unio capitatus Heude, 1874 accepted as Pseudocuneopsis capitata (Heude, 1874)
- Species Unio capsaeformis I. Lea, 1834 accepted as Epioblasma capsaeformis (I. Lea, 1834)
- Species Unio carbonarius I. Lea, 1838 accepted as Barynaias plexus (Conrad, 1838)
- Species Unio carbonarius (Schlotheim, 1820) † accepted as Anthraconaia carbonaria (Schlotheim, 1820) †
- Species Unio cardiacea Guerin, 1823 accepted as Pleurobema rubrum (Rafinesque, 1820)
- Species Unio cardiiformis Blanford, 1883 † accepted as Blanfordinaia cardiiformis (Blanford, 1883) †
- Species Unio cardita Blanford, 1883 † accepted as Indobaphia vicaryi (Blanford, 1883) †
- Species Unio carinatoplicatus Bogachev, 1961 †
- Species Unio carinatus Barnes, 1823 accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio carinifera Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio cariosus Say, 1817 accepted as Lampsilis cariosa (Say, 1817)
- Species Unio carneus Küster, 1854
- Species Unio carolinensis [sic] accepted as Unio caroliniana Bosc, 1801
- Species Unio caroliniana Bosc, 1801 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio carriosoides I. Lea, 1868 † accepted as Lampsilis cariosa (Say, 1817)
- Species Unio carteri Hislop, 1860 † accepted as Lamellidens carteri (Hislop, 1860) †
- Species Unio casaeblancae R. A. Philippi, 1849
- Species Unio castaneus I. Lea, 1831 accepted as Obovaria arkansasensis (I. Lea, 1862)
- Species Unio castelli F. R. Woodward, 1967 †
- Species Unio castor Eichwald, 1861 † accepted as Palaeomutela castor (Eichwald, 1861) †
- Species Unio castus I. Lea, 1860 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio catawbensis I. Lea, 1857 accepted as Unio wheatleyi I. Lea, 1857
- Species Unio catillus Conrad, 1836 accepted as Pleurobema sintoxia (Rafinesque, 1820)
- Species Unio caudiculatus E. von Martens, 1867 accepted as Caudiculatus caudiculatus (E. von Martens, 1867)
- Species Unio caveatus Heude, 1877 accepted as Lamprotula caveata (Heude, 1877)
- Species Unio celtiformis Heude, 1874 accepted as Cuneopsis celtiformis (Heude, 1874)
- Species Unio centralis J. De C. Sowerby, 1840 † accepted as Carbonicola centralis (J. De C. Sowerby, 1823) †
- Species Unio ceratinus Drouët, 1879 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio cerinus Conrad, 1838 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio cetinensis Žagar-Sakač, 1987 †
- Species Unio chantrei Locard, 1883 accepted as Unio delicatus I. Lea, 1863
- Species Unio chaoi Grabau, 1923 † accepted as Unionelloides chaoi (Grabau, 1923) †
- Species Unio charbonnieri Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio charlottensis I. Lea, 1863 accepted as Lasmigona decorata (I. Lea, 1852)
- Species Unio charon Preston, 1910 accepted as Unio caffer Krauss, 1848
- Species Unio charruana A. d'Orbigny, 1835 accepted as Rhipidodonta charruana (A. d'Orbigny, 1835)
- Species Unio chasaricus Bogachev, 1924 †
- Species Unio chathamensis I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio chattanoogaensis I. Lea, 1858 accepted as Pleurobema decisum (I. Lea, 1831)
- Species Unio chickasawhensis I. Lea, 1861 accepted as Pleurobema beadleianum (I. Lea, 1861)
- Species Unio childreni J. E. Gray, 1833 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio chilensis J. E. Gray, 1828 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio chinensis I. Lea, 1868 accepted as Acuticosta chinensis (I. Lea, 1868)
- Species Unio chinnerethensis Preston, 1914 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio chipolaensis B. Walker, 1905 accepted as Elliptio chipolaensis (B. Walker, 1905)
- Species Unio choziensis Preston, 1910 accepted as Coelatura choziensis (Preston, 1910)
- Species Unio chulymensis Lebedev, 1958 † accepted as Proarcidopsis chulymensis (Lebedev, 1958) †
- Species Unio chunii I. Lea, 1862 accepted as Fusconaia chunii (I. Lea, 1861)
- Species Unio churchillianus Bourguignat, 1857 accepted as Pseudodontopsis euphratica (Bourguignat, 1852)
- Species Unio cicatricoides Frierson, 1911 accepted as Plethobasus cicatricosus (Say, 1829)
- Species Unio cicatricosus Say, 1829 accepted as Plethobasus cicatricosus (Say, 1829)
- Species Unio ciconius Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio cicur I. Lea, 1861 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio cilicicus Kobelt & Rolle, 1895 accepted as Unio delicatus I. Lea, 1863
- Species Unio cilindricus Say, 1817 accepted as Unio cylindricus Say, 1817
- Species Unio cincinnatiensis I. Lea, 1840 accepted as Epioblasma cincinnatiensis (I. Lea, 1840)
- Species Unio cinnamomicus I. Lea, 1861 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio circulus I. Lea, 1829 accepted as Obovaria subrotunda Rafinesque, 1820
- Species Unio circumactus I. Lea, 1871 accepted as Pleuronaia dolabelloides (I. Lea, 1840)
- Species Unio cirratus I. Lea, 1874 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio cirtanus Bourguignat, 1862 † accepted as Unio durieui Deshayes, 1847
- Species Unio cistellaeformis I. Lea, 1863 accepted as Elliptio cistellaeformis (I. Lea, 1863)
- Species Unio claibornensis I. Lea, 1838 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio clarkianus I. Lea, 1852 accepted as Hamiota altilis (Conrad, 1834)
- Species Unio clava Lamarck, 1819 accepted as Pleurobema clava (Lamarck, 1819)
- Species Unio clinchensis I. Lea, 1867 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio clinopisthus C. A. White, 1882 † accepted as Elliptio clinopisthus (C. A. White, 1882) †
- Species Unio clinovata Q.-S. Shan, 1994 † accepted as Unio clinovatus Q.-S. Shan, 1994 †
- Species Unio clinovatus Q.-S. Shan, 1994 †
- Species Unio clivosus Brusina, 1874 † accepted as Potomida clivosa (Brusina, 1874) †
- Species Unio coarctata Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio coarctata Anton, 1838
- Species Unio cobalcescui Teisseyre, 1911 †
- Species Unio coccineus Conrad, 1836 accepted as Pleurobema sintoxia (Rafinesque, 1820)
- Species Unio coccineus I. Lea, 1838 accepted as Pleurobema sintoxia (Rafinesque, 1820)
- Species Unio cochlearella Cornuel, 1874 † accepted as Unio cochlearellus Cornuel, 1874 †
- Species Unio cochlearellus Cornuel, 1874 †
- Species Unio cocoduensis Reeve, 1865 accepted as Ligumia subrostrata (Say, 1831)
- Species Unio coelatus Conrad, 1834 accepted as Lemiox rimosus (Rafinesque, 1831)
- Species Unio cognatus I. Lea, 1860 accepted as Truncilla cognata (I. Lea, 1860)
- Species Unio colchaguensis R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio colchicus Drouët, 1881 accepted as Unio crassus Philipsson, 1788
- Species Unio colensis Martinson, 1961 †
- Species Unio collinus Conrad, 1837 accepted as Parvaspina collina (Conrad, 1837)
- Species Unio coloradoensis I. Lea, 1856 accepted as Potamilus purpuratus (Lamarck, 1819)
- Species Unio coloratus Küster, 1856 accepted as Sphenonaias colorata (Küster, 1856)
- Species Unio columbensis I. Lea, 1857 accepted as Uniomerus columbensis (I. Lea, 1857)
- Species Unio comes Bogachev, 1961 †
- Species Unio compactus I. Lea, 1859 accepted as Epioblasma metastriata (Conrad, 1838)
- Species Unio compertus Frierson, 1911 accepted as Plethobasus cyphyus (Rafinesque, 1820)
- Species Unio complanatus ([Lightfoot], 1786) accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio compressa (I. Lea, 1830) accepted as Lasmigona compressa (I. Lea, 1829)
- Species Unio compressissimus I. Lea, 1845 accepted as Ptychobranchus fasciolaris (Rafinesque, 1820)
- Species Unio compressus Rafinesque, 1831 accepted as Ellipsaria lineolata (Rafinesque, 1820)
- Species Unio compressus J. De C. Sowerby, 1828 †
- Species Unio comptus Deshayes, 1876 accepted as Lens comptus (Deshayes, 1876)
- Species Unio computatus Crosse & P. Fischer, 1894 accepted as Actinonaias computata (Crosse & P. Fischer, 1894)
- Species Unio conasaugaensis I. Lea, 1872 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio concavus I. Lea, 1852 accepted as Villosa delumbis (Conrad, 1834)
- Species Unio concentricosculptus G. I. Popov, 1965 †
- Species Unio concestator I. Lea, 1857 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio concinnus J. Sowerby, 1819 † accepted as Cardinia concinna (J. Sowerby, 1819) †
- Species Unio concolor I. Lea, 1861 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio condai Porumbaru, 1881 † accepted as Rugunio condai (Porumbaru, 1881) †
- Species Unio condoni C. A. White, 1885 † accepted as Margaritifera condoni (C. A. White, 1885) †
- Species Unio conemenosi Brusina, 1902 † accepted as Potomida vukasoviciana (Brusina, 1874) †
- Species Unio confertus I. Lea, 1834 accepted as Elliptio raveneli (Conrad, 1834)
- Species Unio congaraeus I. Lea, 1831 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio congareus I. Lea, 1831 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio conjugans B. H. Wright, 1899 accepted as Tritogonia verrucosa (Rafinesque, 1820)
- Species Unio conradicus I. Lea, 1834 accepted as Medionidus conradicus (I. Lea, 1834)
- Species Unio consanguineus I. Lea, 1861 accepted as Pleurobema decisum (I. Lea, 1831)
- Species Unio consentaneus Rossmässler, 1836 accepted as Unio crassus Philipsson, 1788
- Species Unio consobrinus I. Lea, 1860 accepted as Lamellidens generosus (A. Gould, 1847)
- Species Unio conspicuus I. Lea, 1872 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio consuetus Whiteaves, 1885 † accepted as Lampsilis consuetus (Whiteaves, 1885) †
- Species Unio contiguus I. Lea, 1862 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio continentalis (F. Haas, 1910) accepted as Inversidens pantoensis (Neumayr, 1899)
- Species Unio contortus (I. Lea, 1857) accepted as Lanceolaria lanceolata (I. Lea, 1856)
- Species Unio contractus I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio contradens I. Lea, 1838 accepted as Lens contradens (I. Lea, 1838)
- Species Unio contrarius Conrad, 1849 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio contritus Heude, 1881 accepted as Lamprotula caveata (Heude, 1877)
- Species Unio conus Spengler, 1793 accepted as Unio tumidus Philipsson, 1788
- Species Unio convexus F. A. Roemer, 1836 †
- Species Unio cooperianus I. Lea, 1834 accepted as Plethobasus cooperianus (I. Lea, 1834)
- Species Unio copei I. Lea, 1868 accepted as Villosa vanuxemensis (I. Lea, 1838)
- Species Unio copernici Teisseyre, 1907 †
- Species Unio cor Conrad, 1834 accepted as Fusconaia cor (Conrad, 1834)
- Species Unio corbiculiformis Kobelt, 1912 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio corbiculoides Whitfield, 1907 † accepted as Proparreysia corbiculoides (Whitfield, 1907) †
- Species Unio corbis Hanley, 1856 accepted as Indonaia corbis (Hanley, 1856)
- Species Unio cordiformis J. De C. Sowerby, 1828 † accepted as Proparreysia cordiformis (J. De C. Sowerby, 1828) †
- Species Unio coreanus E. von Martens, 1886 accepted as Aculamprotula coreana (E. von Martens, 1886)
- Species Unio coriaceus Dunker, 1849 accepted as Diplodon multistriatus (I. Lea, 1831)
- Species Unio corneus I. Lea, 1874 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio cornueliana A. d'Orbigny, 1850 † accepted as Unio cornuelianus A. d'Orbigny, 1850 †
- Species Unio cornuelianus A. d'Orbigny, 1850 †
- Species Unio cornutus Barnes, 1823 accepted as Obliquaria reflexa Rafinesque, 1820
- Species Unio cornuumlunae Heude, 1883 accepted as Lamprotula cornuumlunae (Heude, 1883)
- Species Unio corrianus I. Lea, 1834 accepted as Lamellidens corrianus (I. Lea, 1834)
- Species Unio corrosus A. Villa & J. B. Villa, 1841 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio corrugatus (O. F. Müller, 1774) accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio coruscus A. Gould, 1856 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio corvinus I. Lea, 1868 accepted as Toxolasma paulum (I. Lea, 1840)
- Species Unio corvunculus I. Lea, 1868 accepted as Toxolasma corvunculus (I. Lea, 1868)
- Species Unio corvus I. Lea, 1859 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio cosmianus Bogachev, 1936 †
- Species Unio costatus Goldfuss, 1837 † accepted as Pseudunio flabellatus (Goldfuss, 1837) †
- Species Unio costatus G. Young & Bird, 1828 † accepted as Pleuromya costata (G. Young & Bird, 1828) †
- Species Unio couchianus I. Lea, 1860 accepted as Quadrula couchiana (I. Lea, 1860)
- Species Unio couesi C. A. White, 1877 † accepted as Ligumia couesi (C. A. White, 1877) †
- Species Unio coulboisi Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio craiovensis Tournouër, 1880 † accepted as Psilunio craiovensis (Tournouër, 1880) †
- Species Unio crapulus I. Lea, 1861 accepted as Pleurobema fibuloides (I. Lea, 1859)
- Species Unio crassidens Lamarck, 1819 accepted as Elliptio crassidens (Lamarck, 1819)
- Species Unio crassidens Ludwig, 1861 † accepted as Carbonicola aquilina (J. De C. Sowerby, 1840) †
- Species Unio crassissimus J. Sowerby, 1817 † accepted as Cardinia crassissima (J. Sowerby, 1817) †
- Species Unio crassiusculus J. Sowerby, 1817 † accepted as Cardinia crassiuscula (J. Sowerby, 1817) †
- Species Unio crassoides Chepalyga, 1967 †
- Species Unio crassulus Drouët, 1888 accepted as Unio crassus Philipsson, 1788
- Species Unio crassus Say, 1817 accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio crassus Philipsson, 1788
- Species Unio crebrivittatus I. Lea, 1861 accepted as Pleurobema decisum (I. Lea, 1831)
- Species Unio cremeri Frech, 1911 † accepted as Eolamprotula cremeri (Frech, 1911) †
- Species Unio creperus I. Lea, 1838 accepted as Villosa iris (I. Lea, 1829)
- Species Unio cretaceus Zittel, 1865 †
- Species Unio cretacollis Maury, 1902 † accepted as Amblema cretacollis (Maury, 1902) †
- Species Unio cretensis H. M. Jenkins, 1864 †
- Species Unio crispata A. Gould, 1843 accepted as Scabies crispata (A. Gould, 1843)
- Species Unio crispisulcatus W. H. Benson, 1862 accepted as Radiatula crispisulcata (W. H. Benson, 1862)
- Species Unio crispisulcatus Bogachev, 1961 † accepted as Rotundaria crispisulcatus (Bogachev, 1961) †
- Species Unio cristonensis Meek, 1875 † accepted as Antediplodon cristonensis (Meek, 1875) †
- Species Unio cristophori Adami, 1886 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio croaticus Drouët, 1881 accepted as Unio crassus Philipsson, 1788
- Species Unio crocatus I. Lea, 1841 accepted as Leptodea ochracea (Say, 1817)
- Species Unio crocodilorum Morelet, 1849 accepted as Psoronaias semigranosa (R. A. Philippi, 1843)
- Species Unio cromwellii I. Lea, 1865 accepted as Toxolasma paulum (I. Lea, 1840)
- Species Unio crossei Deshayes, 1876 accepted as Lens micropterus (Morelet, 1866)
- Species Unio crosthwaitei R. B. Newton, 1909 † accepted as Margaritifera crosthwaitei (R. B. Newton, 1909) †
- Species Unio crudus I. Lea, 1871 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio cryptorhynchus C. A. White, 1877 † accepted as Pleurobema cryptorhynchus (C. A. White, 1877) †
- Species Unio cubranovici Brusina, 1902 †
- Species Unio cucumoides I. Lea, 1840 accepted as Cucumerunio novaehollandiae (Gray, 1834)
- Species Unio cultelliformis Conrad, 1850 accepted as Hyridella depressa (Lamarck, 1819)
- Species Unio cultratus Rafinesque, 1831 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio cumberlandi F. R. Woodward, 1965 †
- Species Unio cumberlandicus I. Lea, 1838 accepted as Cambarunio simus (I. Lea, 1838)
- Species Unio cumingianus Dunker, 1852 accepted as Cucumerunio novaehollandiae (Gray, 1834)
- Species Unio cumingii I. Lea, 1852 accepted as Sinohyriopsis cumingii (I. Lea, 1852)
- Species Unio cuneatus Barnes, 1823 accepted as Elliptio crassidens (Lamarck, 1819)
- Species Unio cuneatus Swainson, 1823 accepted as Epioblasma triquetra (Rafinesque, 1820)
- Species Unio cuneatus Žagar-Sakač, 1987 †
- Species Unio cuneolus I. Lea, 1840 accepted as Fusconaia cuneolus (I. Lea, 1840)
- Species Unio cuneus Conrad, 1838 accepted as Pleurobema sintoxia (Rafinesque, 1820)
- Species Unio cunninghami B. H. Wright, 1883 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio cuprinus I. Lea, 1831 accepted as Popenaias metallica (Say, 1831)
- Species Unio curatus I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio curtus I. Lea, 1859 accepted as Pleurobema curtum (I. Lea, 1859)
- Species Unio curvatus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio cusianus Pini, 1884 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio cuspidatus I. Lea, 1872 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio cuvieri [sic] † accepted as Unio cuvierii Matheron, 1843 †
- Species Unio cuvierianus I. Lea, 1852 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio cuvierii Matheron, 1843 †
- Species Unio cvijici Pavlović, 1931 †
- Species Unio cyamopsis Brusina, 1874 † accepted as Potomida zelebori (M. Hörnes, 1864) †
- Species Unio cyamus R. A. Philippi, 1851 accepted as Unio caffer Krauss, 1848
- Species Unio cylindrellus I. Lea, 1868 accepted as Toxolasma cylindrellum (I. Lea, 1868)
- Species Unio cylindricoides Whitfield, 1907 † accepted as Quadrula cylindricoides (Whitfield, 1907) †
- Species Unio cylindricus Say, 1817 accepted as Theliderma cylindrica (Say, 1817)
- Species Unio cymatoides Brusina, 1874 † accepted as Potomida cymatoides (Brusina, 1874) †
- Species Unio cymbaeformis Ludwig, 1860 †
- Species Unio cyphia (Rafinesque, 1820) accepted as Plethobasus cyphyus (Rafinesque, 1820)
- Species Unio cyprinorum Bourguignat, 1882 accepted as Unio crassus Philipsson, 1788
- Species Unio cyreniformis Oppenheim, 1895 †
- Species Unio cyreniformis Deshayes, 1858 † accepted as Parreysia subtumida (A. d'Orbigny, 1850) †
- Species Unio cyrenoides R. A. Philippi, 1847 accepted as Arotonaias cyrenoides (R. A. Philippi, 1847)
- Species Unio cyrensis K. A. Ali-Zade, 1939 †
- Species Unio cytherea Küster, 1833 accepted as Unio crassus Philipsson, 1788
- Species Unio czekelii Bielz, 1864 †
- Species Unio daanensis Z.-W. Gu & J.-S. Yu, 1999 †
- Species Unio dabberti Modell, 1930 †
- Species Unio dacicus Teisseyre, 1911 †
- Species Unio dactylus I. Lea, 1840 accepted as Cambarunio dactylus dactylus (I. Lea, 1840)
- Species Unio dactylus Morelet, 1845 accepted as Unio delphinus Spengler, 1793
- Species Unio dalli B. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio dalmaticus Drouët, 1879 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio damascensis I. Lea, 1863
- Species Unio danai Meek & Hayden, 1857 † accepted as Fusconaia danai (Meek & Hayden, 1857) †
- Species Unio danellii A. Villa, 1871 accepted as Velesunio ambiguus (R. A. Philippi, 1847)
- Species Unio danielsii B. H. Wright, 1899 accepted as Elliptio crassidens (Lamarck, 1819)
- Species Unio danischi Huckriede, 1967 †
- Species Unio dardanus Calvert & Neumayr, 1880 †
- Species Unio dariensis I. Lea, 1842 accepted as Elliptio dariensis (I. Lea, 1842)
- Species Unio datus I. Lea, 1868 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio dautzenbergi Morlet, 1889 accepted as Lens contradens (I. Lea, 1838)
- Species Unio davilai Porumbaru, 1881 † accepted as Pristinunio davilai (Porumbaru, 1881) †
- Species Unio davilaiformis Chepalyga, 1967 †
- Species Unio dawsoni L. S. Russell, 1931 † accepted as Fusconaia dawsoni (L. S. Russell, 1931) †
- Species Unio dawsoni (T. Brown, 1843) † accepted as Anthracosphaerium dawsoni (T. Brown, 1843) †
- Species Unio deccanensis J. De C. Sowerby, 1840 † accepted as Lamellidens deccanensis (J. De C. Sowerby, 1840) †
- Species Unio decipiens Drouët, 1881 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio decisus I. Lea, 1831 accepted as Pleurobema decisum (I. Lea, 1831)
- Species Unio declivis Say, 1831 accepted as Uniomerus declivis (Say, 1831)
- Species Unio decoratus I. Lea, 1852 accepted as Lasmigona decorata (I. Lea, 1852)
- Species Unio decumbens I. Lea, 1861 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio decurvatus Rossmässler, 1835 accepted as Unio crassus Philipsson, 1788
- Species Unio dehiscens Say, 1829 accepted as Hemistena lata (Rafinesque, 1820)
- Species Unio delesserti Bourguignat, 1852 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio delgadoi Choffat, 1885 †
- Species Unio delicatus I. Lea, 1863
- Species Unio delodonta Lamarck, 1819 accepted as Diplodon delodonta (Lamarck, 1819)
- Species Unio delphinopterus Dautzenberg & Fischer, 1905 accepted as Hyriopsis bialata C. T. Simpson, 1900
- Species Unio delphinulus Morelet, 1849 accepted as Delphinonaias largillierti (R. A. Philippi, 1847)
- Species Unio delphinus Spengler, 1793
- Species Unio delphinus I. Lea, 1840 accepted as Hyriopsis bialata C. T. Simpson, 1900
- Species Unio delphinus Gruner, 1841 accepted as Hyriopsis bialata C. T. Simpson, 1900
- Species Unio delpretei Bourguignat, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio delumbis Conrad, 1834 accepted as Villosa delumbis (Conrad, 1834)
- Species Unio demararaensis I. Lea, 1859 accepted as Diplodon demararaensis (I. Lea, 1859)
- Species Unio dembeae Reeve, 1865
- Species Unio demeraraensis "I. Lea, 1860" accepted as Unio demararaensis I. Lea, 1859
- Species Unio denigratus I. Lea, 1857 accepted as Elliptio nigella (I. Lea, 1852)
- Species Unio depauperata F. W. Hutton, 1883 accepted as Echyridella menziesii (J. E. Gray, 1843)
- Species Unio depolitus Volkova, 1939 †
- Species Unio depressa Lamarck, 1819 accepted as Hyridella depressa (Lamarck, 1819)
- Species Unio depressus Reeve, 1864 accepted as Velesunio moretonicus (Reeve, 1865)
- Species Unio depressus Zieten, 1833 † accepted as Cardinia listeri (J. Sowerby, 1817) †
- Species Unio depygis Conrad, 1866 accepted as Obovaria subrotunda Rafinesque, 1820
- Species Unio deschampsi Kobelt, 1913 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio desectus Westerlund, 1879
- Species Unio deserticus Mongin, 1968 † accepted as Adrarunio deserticus (Mongin, 1968) †
- Species Unio deshayesii Michaud, 1831 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio destremi Porumbaru, 1881 † accepted as Psilunio (Cyclopotomida) destremi (Porumbaru, 1881) †
- Species Unio detectus Frierson, 1911 accepted as Plethobasus cicatricosus (Say, 1829)
- Species Unio deviatus Reeve, 1864 accepted as Epioblasma turgidula (I. Lea, 1858)
- Species Unio deweyanus Meek & Hayden, 1857 † accepted as Fusconaia danai (Meek & Hayden, 1857) †
- Species Unio diarbekirianus Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio diazensis S. H. Wright, 1897 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio didymictidis T. D. A. Cockerell, 1915 † accepted as Actinonaias didymictidis (T. D. A. Cockerell, 1915) †
- Species Unio diespiter Mabille, 1887 accepted as Nodularia diespiter (Mabille, 1887)
- Species Unio differtus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio difficilis I. Lea, 1868 accepted as Villosa nebulosa (Conrad, 1834)
- Species Unio digitatus Morelet, 1851 accepted as Megalonaias nickliniana (I. Lea, 1834)
- Species Unio digitiformis G. B. Sowerby II, 1868
- Species Unio dignatus I. Lea, 1863 accepted as Unio tigridis Bourguignat, 1852
- Species Unio diluvii A. d'Orbigny, 1839 † accepted as Diplodon diluvii (A. d'Orbigny, 1839) †
- Species Unio diminutis I. Lea, 1859 accepted as Unio diminutus I. Lea, 1859
- Species Unio diminutus I. Lea, 1859 accepted as Unio caffer Krauss, 1848
- Species Unio diplodon R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio directus Drouët, 1896 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio discoideus G. B. Sowerby II, 1868
- Species Unio discrepans I. Lea, 1860 accepted as Cambarunio nebulosus (Conrad, 1834)
- Species Unio discrepans T. Brown, 1849 † accepted as Carbonicola discrepans (T. Brown, 1849) †
- Species Unio disculus I. Lea, 1860 accepted as Rhipidodonta funebralis (I. Lea, 1860)
- Species Unio discus I. Lea, 1838 accepted as Disconaias discus (I. Lea, 1838)
- Species Unio dispalans B. H. Wright, 1899 accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio dispansus I. Lea, 1871 accepted as Leaunio vanuxemensis (I. Lea, 1838)
- Species Unio dispar I. Lea, 1860 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio dissimilis I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio distans J. G. Anthony, 1865 accepted as Lampsilis siliquoidea (Barnes, 1823)
- Species Unio distinctus Crosse & P. Fischer, 1893 accepted as Psoronaias distincta (Crosse & P. Fischer, 1893)
- Species Unio distinguendus Lindholm, 1932 † accepted as Nodularia distinguenda (Lindholm, 1932) †
- Species Unio distortus W. Bean, 1836 † accepted as Margaritifera distorta (W. Bean, 1836) †
- Species Unio divaricatus I. Lea, 1834 accepted as Diplodon delodonta (Lamarck, 1819)
- Species Unio diversus Conrad, 1856 accepted as Alasmidonta viridis (Rafinesque, 1820)
- Species Unio dockumensis C. T. Simpson, 1896 † accepted as Antediplodon dockumensis (C. T. Simpson, 1896) †
- Species Unio dolabelloides I. Lea, 1840 accepted as Pleuronaia dolabelloides (I. Lea, 1840)
- Species Unio dolabraeformis I. Lea, 1838 accepted as Lampsilis dolabraeformis (I. Lea, 1838)
- Species Unio dolabratus J. De C. Sowerby, 1840 † accepted as Anthracomya dolabrata (J. De C. Sowerby, 1840) †
- Species Unio doliaris I. Lea, 1865 accepted as Hamiota altilis (Conrad, 1834)
- Species Unio dolichorhynchus Tapparone Canefri, 1889 accepted as Trapezidens dolichorhynchus (Tapparone Canefri, 1889)
- Species Unio doljensis [sic] † accepted as Cuneopsidea doljiensis (Stefanescu, 1896) †
- Species Unio dollfusi Leriche, 1901 †
- Species Unio dolosus I. Lea, 1860 accepted as Potamilus purpuratus (Lamarck, 1819)
- Species Unio dombeyana Valenciennes, 1827 accepted as Plectomerus dombeyanus (Valenciennes, 1827)
- Species Unio donaciformis I. Lea, 1827 accepted as Truncilla donaciformis (I. Lea, 1827)
- Species Unio donacopsis De Gregorio, 1914 accepted as Villosa fabalis (I. Lea, 1831)
- Species Unio dooleyensis I. Lea, 1874 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio dorei B. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio dorfeuillianus I. Lea, 1838 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio dorri Wattebled, 1886 accepted as Nodularia dorri (Wattebled, 1886)
- Species Unio dorsatus I. Lea, 1868 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio dorsatus X.-Z. Liu, 1984 †
- Species Unio dorsuosus A. Gould, 1850 accepted as Hyridella australis (Lamarck, 1819)
- Species Unio douglasiae J. E. Gray, 1833 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio douglassi Stanton, 1903 † accepted as Protelliptio douglassi (Stanton, 1903) †
- Species Unio dowlingi McLearn, 1919 † accepted as Pleurobema dowlingi (McLearn, 1919) †
- Species Unio downiei I. Lea, 1858 accepted as Elliptio downiei (I. Lea, 1858)
- Species Unio dromas I. Lea, 1834 accepted as Dromus dromas (I. Lea, 1834)
- Species Unio dromauxi Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio dubius (T. Brown, 1843) † accepted as Pachyodon dubius T. Brown, 1843 †
- Species Unio dubocqui [sic] † accepted as Pseudunio auricularius (Spengler, 1793)
- Species Unio dubocquii Coquand, 1854 † accepted as Pseudunio auricularius (Spengler, 1793)
- Species Unio duclerci Rochebrune, 1882 accepted as Chamberlainia duclerci (Rochebrune, 1882)
- Species Unio dugasti Morlet, 1892 accepted as Ensidens dugasti (Morlet, 1892)
- Species Unio dujiaensis X.-Z. Liu, 1984 †
- Species Unio dumasi Repelin, 1902 †
- Species Unio dumblei C. T. Simpson, 1896 † accepted as Antediplodon dumblei (C. T. Simpson, 1896) †
- Species Unio dumesnilianus Charmes, 1885 accepted as Coelatura ratidota (Charmes, 1885)
- Species Unio dunkerianus I. Lea, 1856 accepted as Diplodon ellipticus Spix, 1827
- Species Unio dunstani Etheridge, 1888 † accepted as Protovirgus dunstani (Etheridge, 1888) †
- Species Unio duponti Bourguignat, 1883 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio duponti Rochebrune, 1882 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio duregicus Servain, 1886 accepted as Unio crassus Philipsson, 1788
- Species Unio durieui Deshayes, 1847
- Species Unio duttonianus I. Lea, 1841 accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio dysonii I. Lea, 1859 accepted as Nephronaias dysonii (I. Lea, 1859)
- Species Unio eagari F. R. Woodward, 1964 †
- Species Unio ebenus I. Lea, 1831 accepted as Reginaia ebenus (I. Lea, 1831)
- Species Unio eberzini Jatsko, 1955 † accepted as Psilunio eberzini (Jatsko, 1955) †
- Species Unio ectatus Fontannes, 1880 †
- Species Unio edentulus (Say, 1829) accepted as Strophitus undulatus (Say, 1817)
- Species Unio edgarianus I. Lea, 1840 accepted as Fusconaia cor (Conrad, 1834)
- Species Unio edwardsi [sic] † accepted as Unio edwardsii S. V. Wood, 1864 †
- Species Unio edwardsianus Bourguignat, 1883 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio edwardsii S. V. Wood, 1864 †
- Species Unio edwini B. B. Gupta, 1930 †
- Species Unio effulgens I. Lea, 1856 accepted as Diplodon multistriatus (I. Lea, 1831)
- Species Unio ehrmanni Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio eibiswaldensis Stur, 1871 †
- Species Unio eichwaldianus Verneuil, 1845 † accepted as Palaeomutela eichwaldiana (Verneuil, 1845) †
- Species Unio eightsii I. Lea, 1860 accepted as Megalonaias nervosa (Rafinesque, 1820)
- Species Unio electrinus Reeve, 1865 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio elegans I. Lea, 1831 accepted as Truncilla truncata Rafinesque, 1820
- Species Unio elliottii I. Lea, 1857 accepted as Amblema elliottii (I. Lea, 1857)
- Species Unio ellipsiformis Conrad, 1836 accepted as Venustaconcha ellipsiformis (Conrad, 1836)
- Species Unio ellipsis I. Lea, 1827 accepted as Obovaria olivaria (Rafinesque, 1820)
- Species Unio ellipsoideus Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio ellipticus Barnes, 1823 accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio ellipticus B.-L. Ding & J.-H. Li, 1982 †
- Species Unio elongata Lamarck, 1819 accepted as Unio elongatus Lamarck, 1819
- Species Unio elongata Cornuel, 1874 †
- Species Unio elongatulus C. Pfeiffer, 1825
- Species Unio elongatus Lamarck, 1819 accepted as Margaritifera margaritifera (Linnaeus, 1758)
- Species Unio elongatus Martinson, 1961 † accepted as Unio transbaicalensis Martinson, 1961 †
- Species Unio emarginatus I. Lea, 1834 accepted as Unio mancus Lamarck, 1819
- Species Unio embletoni (T. Brown, 1843) † accepted as Carbonicola embletoni (T. Brown, 1843) †
- Species Unio emersoni Troxell, 1914 †
- Species Unio emesaensis I. Lea, 1865 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio emigrans Bogachev, 1924 †
- Species Unio emini E. von Martens, 1897 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio emmonsii I. Lea, 1857 accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio encarpus I. Lea, 1868 accepted as Arotonaias imbricata (Mörch, 1861)
- Species Unio endlichi C. A. White, 1877 † accepted as Margaritifera endlichi (C. A. White, 1877) †
- Species Unio eomargaron T. D. A. Cockerell, 1915 † accepted as Elliptio eomargaron (T. D. A. Cockerell, 1915) †
- Species Unio epigonus Bogachev, 1961 †
- Species Unio episcopalis Tristram, 1865 accepted as Pseudunio homsensis (I. Lea, 1865)
- Species Unio erevanica Radopulo, 1953 †
- Species Unio errans I. Lea, 1857 accepted as Elliptio errans (I. Lea, 1857)
- Species Unio eseri Krauss, 1852 †
- Species Unio essoensis Chaper, 1885 accepted as Coelatura essoensis (Chaper, 1885)
- Species Unio estabrookianus I. Lea, 1845 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio estabrookii "I. Lea, 1868" accepted as Unio estabrookianus I. Lea, 1845
- Species Unio etheridgei R. M. Johnston, 1888 †
- Species Unio etruscus D'Ancona, 1867 †
- Species Unio eucallistellus Bourguignat, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio eucirrus Bourguignat, 1857
- Species Unio euliratus Rafinesque, 1831 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio euphraticus Bourguignat, 1852 accepted as Pseudodontopsis euphratica (Bourguignat, 1852)
- Species Unio euphymus Charmes, 1885 accepted as Coelatura ratidota (Charmes, 1885)
- Species Unio euryssellinus Pallary, 1902
- Species Unio evanescens Mousson, 1849 accepted as Lamellidens marginalis (Lamarck, 1819)
- Species Unio evitatus I. Lea, 1866 accepted as Indonaia caerulea (I. Lea, 1831)
- Species Unio exactus I. Lea, 1858 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio exacutus I. Lea, 1872 accepted as Elliptio folliculata (I. Lea, 1838)
- Species Unio exanthematicus Küster, 1861 accepted as Pressidens exanthematicus (Küster, 1861)
- Species Unio excavatus I. Lea, 1857 accepted as Lampsilis ornata (Conrad, 1835)
- Species Unio excentricus Brusina, 1874 † accepted as Cuneopsidea oriovacensis (M. Hörnes, 1864) †
- Species Unio excultus Conrad, 1838 accepted as Uniomerus declivis (Say, 1831)
- Species Unio exiguus I. Lea, 1840 accepted as Villosa vibex (Conrad, 1834)
- Species Unio exilis Dunker, 1846 accepted as Lens contradens (I. Lea, 1838)
- Species Unio eximius I. Lea, 1856 accepted as Lens eximius (I. Lea, 1856)
- Species Unio exolescens A. Gould, 1843 accepted as Trapezidens exolescens (A. Gould, 1843)
- Species Unio exoletus (T. Brown, 1843) † accepted as Carbonicola acuta (J. Sowerby, 1813) †
- Species Unio expansus Küster, 1856 accepted as Diplodon multistriatus (I. Lea, 1831)
- Species Unio explicatus Morelet, 1849 accepted as Cyrtonaias explicata (Morelet, 1849)
- Species Unio extensus I. Lea, 1857 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio eyrensis Etheridge, 1892 † accepted as Prohyria eyrensis (Etheridge, 1892) †
- Species Unio faba A. d'Orbigny, 1835 accepted as Diplodon charruanus (A. d'Orbigny, 1835)
- Species Unio fabaceus I. Lea, 1861 accepted as Villosa umbrans (I. Lea, 1857)
- Species Unio fabagina Deshayes, 1876 accepted as Unionetta fabagina (Deshayes, 1876)
- Species Unio fabalis I. Lea, 1831 accepted as Paetulunio fabalis (I. Lea, 1831)
- Species Unio fallax I. Lea, 1857 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio famelicus A. Gould, 1850 accepted as Diplodon granosus (Bruguière, 1792)
- Species Unio fangcunensis B.-Y. Huang & J.-H. Chen, 1980 † accepted as Eocuneopsis thailandica (Hayami, 1968) †
- Species Unio farri Stanton, 1903 † accepted as Lampsilis farri (Stanton, 1903) †
- Species Unio fascellinus Locard, 1882 accepted as Unio mancus Lamarck, 1819
- Species Unio fasciata Rafinesque, 1820 accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio fassinans I. Lea, 1868 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio fatuus I. Lea, 1840 accepted as Villosa iris (I. Lea, 1829)
- Species Unio favidens W. H. Benson, 1862 accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio favosus I. Lea, 1857 accepted as Pleurobema georgianum (I. Lea, 1841)
- Species Unio favrei Locard, 1893 † accepted as Psilunio favrei (Locard, 1893) †
- Species Unio fayumensis Pilsbry & Bequaert, 1927 † accepted as Unio abyssinicus E. von Martens, 1866
- Species Unio feae Tapparone Canefri, 1889 accepted as Leoparreysia tavoyensis (A. Gould, 1843)
- Species Unio feddeni Theobald, 1873 accepted as Leoparreysia feddeni (Theobald, 1873)
- Species Unio felchi [sic] † accepted as Eurynia felchii (C. A. White, 1886) †
- Species Unio felchii C. A. White, 1886 † accepted as Eurynia felchii (C. A. White, 1886) †
- Species Unio fellmanni Deshayes, 1848 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio ferrissii W. A. Marsh, 1891 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio fibrosus Heude, 1877 accepted as Aculamprotula fibrosa (Heude, 1877)
- Species Unio fibuloides I. Lea, 1859 accepted as Pleurobema fibuloides (I. Lea, 1859)
- Species Unio filiferus Bogachev, 1961 †
- Species Unio firmus I. Lea, 1866 accepted as Diplodon delodonta (Lamarck, 1819)
- Species Unio fiscallianus Kobelt, 1873 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio fischerianus Morlet, 1883 accepted as Lens micropterus (Morelet, 1866)
- Species Unio fisherianus I. Lea, 1838 accepted as Elliptio fisheriana (I. Lea, 1838)
- Species Unio fissidentatus Lindholm, 1932 † accepted as Cuneopsis fissidentata (Lindholm, 1932) †
- Species Unio flabellatiformis Grigorovich-Beresovskiy, 1915 † accepted as Pseudunio flabellatiformis (Grigorovich-Beresovskiy, 1915) †
- Species Unio flabellatus Goldfuss, 1837 † accepted as Pseudunio flabellatus (Goldfuss, 1837) †
- Species Unio flabelliferus Noulet, 1846 † accepted as Margaritifera (Pseudunio) flabellata (Goldfuss, 1837) †
- Species Unio flagellatus Say, 1830 accepted as Epioblasma obliquata (Rafinesque, 1820)
- Species Unio flavescens I. Lea, 1845 accepted as Ptychobranchus greenii (Conrad, 1834)
- Species Unio flavidens [sic] accepted as Unio favidens W. H. Benson, 1862
- Species Unio flavidulus I. Lea, 1861 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio flavidus I. Lea, 1872 accepted as Fusconaia cuneolus (I. Lea, 1840)
- Species Unio flexicostata Gümbel, 1861 † accepted as Psilunio flexicostatus (Gümbel, 1861) †
- Species Unio florentinus I. Lea, 1857 accepted as Epioblasma florentina (I. Lea, 1857)
- Species Unio floridensis I. Lea, 1852 accepted as Lampsilis floridensis (I. Lea, 1852)
- Species Unio fluctiger I. Lea, 1859
- Species Unio fluminalis Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio fluviatilis Green, 1827 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio foetterlei †
- Species Unio fokkesi Dunker, 1852 accepted as Diplodon delodontus (Lamarck, 1819)
- Species Unio foliacea A. Gould, 1843 accepted as Unio foliaceus A. Gould, 1843
- Species Unio foliaceus A. Gould, 1843 accepted as Trapezoideus foliaceus (A. Gould, 1843)
- Species Unio foliatus Hildreth, 1828 accepted as Epioblasma flexuosa (Rafinesque, 1820)
- Species Unio folliculatus I. Lea, 1838 accepted as Elliptio folliculata (I. Lea, 1838)
- Species Unio foncki R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio fontainiana A. d'Orbigny, 1835 accepted as Diplodon fontainianus (A. d'Orbigny, 1835)
- Species Unio fontanus Conrad, 1866 accepted as Leaunio lienosus caliginosus (I. Lea, 1845)
- Species Unio footei Theobald, 1876 accepted as Arcidopsis footei (Theobald, 1876)
- Species Unio forbesianus I. Lea, 1852 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio foremanianus I. Lea, 1842 accepted as Ptychobranchus foremanianus (I. Lea, 1842)
- Species Unio formosus I. Lea, 1831 accepted as Epioblasma triquetra (Rafinesque, 1820)
- Species Unio forsheyi I. Lea, 1859 accepted as Quadrula apiculata (Say, 1829)
- Species Unio foucauldianus Pallary, 1936
- Species Unio fourtaui Pallary, 1902
- Species Unio fragilis G. Nevill, 1877 accepted as Lens pallegoixi (G. B. Sowerby II, 1867)
- Species Unio fragosus Conrad, 1835 accepted as Quadrula fragosa (Conrad, 1835)
- Species Unio fragrosus accepted as Quadrula fragosa (Conrad, 1835)
- Species Unio framesi (Connolly, 1925) accepted as Coelatura mossambicensis framesi (Connolly, 1925)
- Species Unio franconica Dehm, 1935 † accepted as Unio franconicus Dehm, 1935 †
- Species Unio franconicus Dehm, 1935 †
- Species Unio frankenbergeri Petrbok, 1923 †
- Species Unio fraternus I. Lea, 1852 accepted as Elliptio fraterna (I. Lea, 1852)
- Species Unio frenzelii Ihering, 1893 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio friersoni B. H. Wright, 1896 accepted as Pleurobema riddellii (I. Lea, 1862)
- Species Unio fruhstorferi Dautzenberg, 1900 accepted as Lanceolaria fruhstorferi (Dautzenberg, 1900)
- Species Unio fryanus B. H. Wright, 1888 accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio fucatus I. Lea, 1860 accepted as Villosa taeniata (Conrad, 1834)
- Species Unio fuchsi Penecke, 1883 † accepted as Hyriopsis fuchsi (Penecke, 1883) †
- Species Unio fulgidus I. Lea, 1845 accepted as Pleurobema sintoxia (Rafinesque, 1820)
- Species Unio fuliginosus I. Lea, 1845 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio fuligo Reeve, 1865 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio fulvaster Drouët & Chaper, 1892 accepted as Lens lugens (Drouët & Chaper, 1892)
- Species Unio fulvus I. Lea, 1834 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio fumatus I. Lea, 1857 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio funebralis I. Lea, 1860 accepted as Rhipidodonta funebralis (I. Lea, 1860)
- Species Unio fungcunensis [sic] † accepted as Eocuneopsis thailandica (Hayami, 1968) †
- Species Unio furvus Conrad, 1834 accepted as Pleurobema rubellum (Conrad, 1834)
- Species Unio fuscatus I. Lea, 1843 accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio fusculus Rossmässler, 1835 accepted as Unio crassus Philipsson, 1788
- Species Unio fusseneggeri Modell, 1934 †
- Species Unio gabbianus I. Lea, 1868 accepted as Arotonaias gabbianus (I. Lea, 1868)
- Species Unio gabonensis Küster, 1862 accepted as Coelatura gabonensis (Küster, 1862)
- Species Unio galeatus Ragozin, 1954 †
- Species Unio galilaei Locard, 1883 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio gallinensis Meek, 1875 † accepted as Antediplodon gallinensis (Meek, 1875) †
- Species Unio galloprovincialis Matheron, 1843 † accepted as Dentaspatharia galloprovincialis (Matheron, 1843) †
- Species Unio gandavensis Leriche, 1901 †
- Species Unio gangrenosus J. F. Schmidt, 1840 accepted as Unio crassus Philipsson, 1788
- Species Unio ganquanensis J.-S. Yu, 1980 †
- Species Unio gardanensis Matheron, 1843 †
- Species Unio gardneri Stanton, 1916 † accepted as Proparreysia gardneri (Stanton, 1916) †
- Species Unio garumnica L. M. Vidal, 1921 † accepted as Unio garumnicus L. M. Vidal, 1921 †
- Species Unio garumnicus L. M. Vidal, 1921 †
- Species Unio gassiei Küster, 1856 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio gastonensis I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio gaudichaudii Eydoux, 1838 accepted as Indonaia caerulea (I. Lea, 1831)
- Species Unio gaudioni Drouët, 1881 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio geddingsianus I. Lea, 1840 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio geinitzi Ludwig, 1861 †
- Species Unio geminus I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio generosus A. Gould, 1847 accepted as Lamellidens generosus (A. Gould, 1847)
- Species Unio genezarethanus Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio genthii I. Lea, 1857 accepted as Villosa constricta (Conrad, 1838)
- Species Unio gentilis F. Haas, 1911 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio genuinus I. Lea, 1868 accepted as Villosa delumbis (Conrad, 1834)
- Species Unio geometricus I. Lea, 1834 accepted as Uniomerus declivis (Say, 1831)
- Species Unio georgianus I. Lea, 1841 accepted as Pleurobema georgianum (I. Lea, 1841)
- Species Unio georgina Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio geranicus K. A. Ali-Zade, 1939 †
- Species Unio gerardi (T. Brown, 1843) † accepted as Pachyodon gerardi T. Brown, 1843 †
- Species Unio gerbidoni Eydoux, 1838 accepted as Indonaia caerulea (I. Lea, 1831)
- Species Unio gereti Preston, 1910 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio gerhardtii I. Lea, 1862 accepted as Hamiota altilis (Conrad, 1834)
- Species Unio germanus I. Lea, 1861 accepted as Toxolasma paulum (I. Lea, 1840)
- Species Unio gerrardi E. von Martens, 1897 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio gerstfeldtianus Clessin, 1880 accepted as Unio tumidus Philipsson, 1788
- Species Unio gesneri [sic] accepted as Unio gesnerii I. Lea, 1874
- Species Unio gesnerii I. Lea, 1874 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio geticus Ionescu-Argetoaia, 1918 † accepted as Psilunio (Cyclopotomida) munieri (Stefanescu, 1896) †
- Species Unio gianellii Tapparone Canefri, 1889 accepted as Trapezidens dolichorhynchus (Tapparone Canefri, 1889)
- Species Unio gibber I. Lea, 1838 accepted as Pleuronaia gibber (I. Lea, 1838)
- Species Unio gibbesianus I. Lea, 1852 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio gibbosoides Whitfield, 1907 † accepted as Plesielliptio stantoni (C. A. White, 1907) †
- Species Unio gibbosus Barnes, 1823 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio gibbsii Forbes, 1856 †
- Species Unio gibbus Spengler, 1793
- Species Unio giganteus Barnes, 1823 accepted as Megalonaias nervosa (Rafinesque, 1820)
- Species Unio giganteus D.-Y. Wang, 1977 †
- Species Unio gigas Swainson, 1824 accepted as Lasmigona complanata (Barnes, 1823)
- Species Unio gigliolii Brusina, 1902 † accepted as Potomida stachei (Neumayr, 1875) †
- Species Unio glaber I. Lea, 1838 accepted as Villosa iris (I. Lea, 1829)
- Species Unio glabrata Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio gladiator Ancey, 1881 accepted as Nodularia gladiator (Ancey, 1881)
- Species Unio gladiolus Heude, 1877 accepted as Lanceolaria gladiola (Heude, 1877)
- Species Unio glandaceus I. Lea, 1861 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio glans I. Lea, 1831 accepted as Toxolasma lividum Rafinesque, 1831
- Species Unio glaucinus Porro, 1838 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio glebulus Say, 1831 accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio glenelgensis Dennant, 1898 accepted as Hyridella glenelgensis (Dennant, 1898)
- Species Unio globatus I. Lea, 1871 accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio goascoranensis I. Lea, 1858 accepted as Nephronaias goascoranensis (I. Lea, 1858)
- Species Unio goldfussanus [sic] † accepted as Palaeomutela goldfussiana (de Koninck, 1841) †
- Species Unio golovae Lebedev, 1958 †
- Species Unio goniambonatus C. A. White, 1878 † accepted as Amblema goniambonatus (C. A. White, 1878) †
- Species Unio gonionotus C. A. White, 1876 † accepted as Amblema gonionotus (C. A. White, 1876) †
- Species Unio gontierii Bourguignat, 1856
- Species Unio gorjenis Teisseyre, 1911 † accepted as Potomida gorjensis (Teisseyre, 1911) †
- Species Unio gottschei E. von Martens, 1894 accepted as Lamprotula gottschei (E. von Martens, 1894)
- Species Unio gouldi [sic] accepted as Villosa lienosa (Conrad, 1834)
- Species Unio gouldii I. Lea, 1845 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio gowhattensis Theobald, 1873 accepted as Parreysia marcens (W. H. Benson, 1862)
- Species Unio grabaui Martinson, 1956 †
- Species Unio gracilentus I. Lea, 1857 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio gracilior I. Lea, 1857 accepted as Villosa vibex (Conrad, 1834)
- Species Unio graciliratus C. T. Simpson, 1896 † accepted as Antediplodon graciliratus (C. T. Simpson, 1896) †
- Species Unio gracilis Barnes, 1823 accepted as Leptodea fragilis (Rafinesque, 1820)
- Species Unio gracillior "I. Lea, 1858" accepted as Unio gracilior I. Lea, 1857
- Species Unio graeteri Kobelt, 1913 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio graeteri Kobelt, 1912 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio granadensis I. Lea, 1868 accepted as Micronaias granadensis (I. Lea, 1868)
- Species Unio granadensis [sic] accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio grandensis Conrad, 1855 accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio grandidens I. Lea, 1862 accepted as Aculamprotula grandidens (I. Lea, 1862)
- Species Unio grandidieri Bourguignat, 1883 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio grandis Zieten, 1833 † accepted as Anodonta splendens (Goldfuss, 1837) †
- Species Unio grangeri T. D. A. Cockerell, 1915 † accepted as Lampsilis grangeri (T. D. A. Cockerell, 1915) †
- Species Unio graniferus (I. Lea, 1838) accepted as Rotundaria tuberculata (Rafinesque, 1820)
- Species Unio granosa Bruguière, 1792 accepted as Diplodon granosus (Bruguière, 1792)
- Species Unio grantianus Bourguignat, 1883 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio granulatis I. Lea, 1861 accepted as Unio granulatus I. Lea, 1861
- Species Unio granulatus I. Lea, 1861
- Species Unio granuliferus Dunker, 1849 accepted as Diplodon multistriatus (I. Lea, 1831)
- Species Unio gratiosus R. A. Philippi, 1843 accepted as Indonaia gratiosa (R. A. Philippi, 1843)
- Species Unio gratus I. Lea, 1860 accepted as Diplodon gratus (I. Lea, 1860)
- Species Unio gravidus I. Lea, 1856 accepted as Physunio superbus (I. Lea, 1843)
- Species Unio grayanus I. Lea, 1834 accepted as Lanceolaria grayana (I. Lea, 1834)
- Species Unio grayii J. E. Gray, 1833 accepted as Lanceolaria grayii (J. E. Gray, 1833)
- Species Unio gredleri Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio gredleri Adami, 1886 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio greeffeanus Ihering, 1893 accepted as Diplodon greeffeanus (Ihering, 1893)
- Species Unio greenii Conrad, 1834 accepted as Ptychobranchus greenii (Conrad, 1834)
- Species Unio gregorii Kobelt, 1911 accepted as Unio crassus Philipsson, 1788
- Species Unio grelloisianus Bourguignat, 1856 accepted as Unio terminalis Bourguignat, 1852
- Species Unio griffithianus I. Lea, 1834 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio grippi Pavlović, 1931 †
- Species Unio gualterii J. De C. Sowerby, 1836 † accepted as Protelliptio gualterii (J. De C. Sowerby, 1836) †
- Species Unio guangyuanensis Q.-H. Ma, 1984 † accepted as Eocuneopsis guangyuanensis (Q.-H. Ma, 1984) †
- Species Unio guaraniana A. d'Orbigny, 1835 accepted as Diplodon guaranianus (A. d'Orbigny, 1835)
- Species Unio gubernaculum Reeve, 1865 accepted as Epioblasma gubernaculum (Reeve, 1865)
- Species Unio gudal Bogachev, 1908 † accepted as Bogatschevia gudal (Bogachev, 1908) †
- Species Unio guillemeti Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio gundlachi Dunker, 1858 accepted as Nephronaias gundlachi (Dunker, 1858)
- Species Unio guppyi E. A. Smith, 1885 accepted as Hyridella guppyi (E. A. Smith, 1885)
- Species Unio gurkensis Bourguignat, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio haeckeli Penecke, 1883 †
- Species Unio haessleini Modell, 1935 †
- Species Unio hageni Strubell, 1897 accepted as Lens contradens (I. Lea, 1838)
- Species Unio hagnei C. T. Simpson, 1900 accepted as Contradens contradens (I. Lea, 1838)
- Species Unio hainesianus I. Lea, 1856 accepted as Chamberlainia hainesiana (I. Lea, 1856)
- Species Unio halavatsi Brusina, 1902 † accepted as Unio mihanovici Brusina, 1896 †
- Species Unio haleianus I. Lea, 1842 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio halepensis Kobelt, 1913 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio halepensis Kobelt, 1912 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio hallenbeckii I. Lea, 1859 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio hamburgiensis Servain, 1888 accepted as Unio crassus Philipsson, 1788
- Species Unio hamili McLearn, 1929 † accepted as Protelliptio hamili (McLearn, 1929) †
- Species Unio hamyanus Bourguignat, 1885 accepted as Unio dembeae Reeve, 1865
- Species Unio hanganensis Yakushina, 1973 †
- Species Unio hanleyianus I. Lea, 1852 accepted as Pleurobema hanleyianum (I. Lea, 1852)
- Species Unio harperi B. H. Wright, 1899 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio hartmanianus I. Lea, 1860 accepted as Pleurobema hartmanianum (I. Lea, 1860)
- Species Unio hartwrightii B. H. Wright, 1896 accepted as Elliptio monroensis (I. Lea, 1843)
- Species Unio hasnotensis (H. E. Vokes, 1935) † accepted as Nannonaia hasnotensis (H. E. Vokes, 1935) †
- Species Unio hastatus I. Lea, 1874 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio haueri Neumayr, 1875 † accepted as Cuneopsidea haueri (Neumayr, 1875) †
- Species Unio hauttecoeuri Bourguignat, 1883 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio haydeni Meek, 1860 † accepted as Elliptio haydeni (Meek, 1860) †
- Species Unio haysianus I. Lea, 1834 accepted as Epioblasma haysiana (I. Lea, 1834)
- Species Unio hazelhurstianus I. Lea, 1858 accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio hazlehurstianus I. Lea, 1858 accepted as Unio hazelhurstianus I. Lea, 1858
- Species Unio heberti Cobălcescu, 1883 † accepted as Chersonimactra bulgarica (Toula, 1892) †
- Species Unio heberti Choffat, 1885 †
- Species Unio hebes I. Lea, 1852 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio hebetatus Conrad, 1854 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio hedeius Mabille, 1889 accepted as Nodularia micheloti (Morlet, 1886)
- Species Unio heermannii I. Lea, 1862 accepted as Cyrtonaias tampicoensis (I. Lea, 1838)
- Species Unio heilongjiangensis Sha & Fürsich, 1993 † accepted as Unio longus (G.-X. Zhu, 1976) †
- Species Unio heimi Choffat, 1885 †
- Species Unio heldii Küster, 1854 accepted as Unio crassus Philipsson, 1788
- Species Unio heldreichi O. Boettger, 1886 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio helenae Drouët, 1892 accepted as Unio ionicus Drouët, 1879
- Species Unio hembeli Conrad, 1838 accepted as Margaritifera hembeli (Conrad, 1838)
- Species Unio hepaticus I. Lea, 1859 accepted as Elliptio hepatica (I. Lea, 1859)
- Species Unio heres Neumayr, 1899 accepted as Rhombuniopsis heres (Neumayr, 1899)
- Species Unio herjei Porumbaru, 1881 † accepted as Potomida herjei (Porumbaru, 1881) †
- Species Unio herodes Kobelt & Rolle, 1895 accepted as Unio terminalis Bourguignat, 1852
- Species Unio heros Say, 1829 accepted as Megalonaias nervosa (Rafinesque, 1820)
- Species Unio heterodon I. Lea, 1829 accepted as Prolasmidonta heterodon (I. Lea, 1829)
- Species Unio heudei Heude, 1874 accepted as Cuneopsis heudei (Heude, 1874)
- Species Unio hians Valenciennes, 1827 accepted as Alasmidonta undulata (Say, 1817)
- Species Unio hians Jatsko, 1954 †
- Species Unio higginsii I. Lea, 1857 accepted as Ortmanniana higginsii (I. Lea, 1857)
- Species Unio hilberi Penecke, 1883 † accepted as Unio kukuljevici Brusina, 1878 †
- Species Unio hildrethi Delessert, 1841 accepted as Hemistena lata (Rafinesque, 1820)
- Species Unio hildrethianus I. Lea, 1834 accepted as Simpsonaias ambigua (Say, 1825)
- Species Unio hinkleyi B. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio hinschi "Modell, 1864" †
- Species Unio hippopoeus I. Lea, 1845 accepted as Amblema plicata (Say, 1817)
- Species Unio hippopotami Bourguignat, 1869 † accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio hispalensis Kobelt, 1888 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio hispanus Rossmässler, 1844 accepted as Unio delphinus Spengler, 1793
- Species Unio hjalmarsoni Dunker, 1858 accepted as Nephronaias hjalmarsoni (Dunker, 1858)
- Species Unio hocaensis Milošević, 1968 †
- Species Unio hocensis [sic] † accepted as Unio hocaensis Milošević, 1968 †
- Species Unio hochstetteri Dunker, 1862 accepted as Echyridella menziesii (J. E. Gray, 1843)
- Species Unio hochstetteri Neumayr, 1875 † accepted as Cuneopsidea oriovacensis (M. Hörnes, 1864) †
- Species Unio hoctemberiani Aslanyan, 1970 †
- Species Unio hoctemberjanensis [sic] † accepted as Unio hoctemberiani Aslanyan, 1970 †
- Species Unio hoernesi Penecke, 1883 †
- Species Unio holmesianus C. A. White, 1877 † accepted as Proparreysia holmesiana (C. A. White, 1877) †
- Species Unio holstonensis I. Lea, 1840 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio homsensis I. Lea, 1865 accepted as Pseudunio homsensis (I. Lea, 1865)
- Species Unio hopetonensis I. Lea, 1838 accepted as Elliptio hopetonensis (I. Lea, 1838)
- Species Unio horei E. A. Smith, 1880 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio hornschuchi H. A. C. Berger, 1854 †
- Species Unio houngdarauicus Tapparone Canefri, 1889 accepted as Leoparreysia tavoyensis (A. Gould, 1843)
- Species Unio housei I. Lea, 1856 accepted as Hyriopsis myersiana (I. Lea, 1856)
- Species Unio houstonensis I. Lea, 1859 accepted as Pustulosa pustulosa (I. Lea, 1831)
- Species Unio hrazdanica Radopulo, 1953 †
- Species Unio huainingensis B.-Y. Huang, J.-H. Li & B.-L. Ding, 1980 †
- Species Unio huangbogouensis Hua, 1965 †
- Species Unio huangbongouensis [sic] † accepted as Unio huangbogouensis Hua, 1965 †
- Species Unio hubbardii Gabb, 1869 † accepted as Elliptio hubbardii (Gabb, 1869) †
- Species Unio hueti Bourguignat, 1855
- Species Unio hulukouensis X.-Z. Liu, 1981 †
- Species Unio humatus Mabille, 1889
- Species Unio humei R. B. Newton, 1909 † accepted as Tegulaedon humei (R. B. Newton, 1909) †
- Species Unio humei Dyer, 1930 † accepted as Pleurobema humei (Dyer, 1930) †
- Species Unio humerosoides I. Lea, 1868 † accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio humerosus I. Lea, 1868 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio humerosus Westerlund, 1890 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio humilior Lindholm, 1932 † accepted as Cuneopsis humilior (Lindholm, 1932) †
- Species Unio humilis I. Lea, 1856 accepted as Radiatula humilis (I. Lea, 1856)
- Species Unio hunteri Hislop, 1860 † accepted as Indonaia hunteri (Hislop, 1860) †
- Species Unio hyalinus I. Lea, 1845 accepted as Lasmigona subviridis (Conrad, 1835)
- Species Unio hybrida J. Sowerby, 1817 † accepted as Cardinia listeri (J. Sowerby, 1817) †
- Species Unio hybrida Bogachev, 1961 †
- Species Unio hydianus I. Lea, 1838 accepted as Lampsilis hydiana (I. Lea, 1838)
- Species Unio hylaea A. d'Orbigny, 1835 accepted as Diplodon hylaeus (A. d'Orbigny, 1835)
- Species Unio hyperamblius Kobelt, 1912 accepted as Unio tigridis Bourguignat, 1852
- Species Unio hypsiprymnus E. von Martens, 1897 accepted as Coelatura hypsiprymna (E. von Martens, 1897)
- Species Unio ianthinus R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio iconomianus Tournouër, 1880 † accepted as Cuneopsidea iconomiana (Tournouër, 1880) †
- Species Unio icterinus Conrad, 1834 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio idrinus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio idubedae Palacios & R. Sánchez, 1885 † accepted as Paraheudeana idubedae (Palacios & R. Sánchez, 1885) †
- Species Unio iheringi B. H. Wright, 1898 accepted as Fusconaia iheringi (B. H. Wright, 1898)
- Species Unio ilqi Bourguignat, 1885 accepted as Unio dembeae Reeve, 1865
- Species Unio imbricatus Mörch, 1861 accepted as Arotonaias imbricata (Mörch, 1861)
- Species Unio imbricatus Hislop, 1860 † accepted as Parreysia imbricata (Hislop, 1860) †
- Species Unio imkelleri Modell, 1931 †
- Species Unio immutatus Martinson, 1951 † accepted as Acuticosta immutata (Martinson, 1951) †
- Species Unio imperialis Morelet, 1863 accepted as Chamberlainia hainesiana (I. Lea, 1856)
- Species Unio imperitus De Gregorio, 1914 accepted as Ptychobranchus fasciolaris (Rafinesque, 1820)
- Species Unio inaequalis Rochebrune, 1882 accepted as Lens micropterus (Morelet, 1866)
- Species Unio inaequiradiatus Gümbel, 1861 † accepted as Margaritifera inaequiradiata (Gümbel, 1861) †
- Species Unio incerta de Serres, 1853 †
- Species Unio incrassatus I. Lea, 1840 accepted as Elliptio crassidens (Lamarck, 1819)
- Species Unio incurvus I. Lea, 1831 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio incurvus Bogachev, 1961 †
- Species Unio indefinilus I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio indefinitus "I. Lea, 1866" accepted as Unio indefinilus I. Lea, 1863
- Species Unio indefinitus F. Haas, 1969 accepted as Unio indefinilus I. Lea, 1863
- Species Unio indifferens Lindholm, 1932 †
- Species Unio ineptus I. Lea, 1852 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio inflata F. W. Hutton, 1873 † accepted as Echyridella huttoni (McMichael, 1957) †
- Species Unio inflata Hecart, 1833 accepted as Unio tumidus Philipsson, 1788
- Species Unio inflatus Barnes, 1823 accepted as Lampsilis siliquoidea (Barnes, 1823)
- Species Unio inflatus Studer, 1820 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio inflatus Gümbel, 1861 † accepted as Psilunio flexicostatus (Gümbel, 1861) †
- Species Unio infrarostratus Schepman, 1896 accepted as Caudiculatus caudiculatus (E. von Martens, 1867)
- Species Unio infucatus Conrad, 1834 accepted as Rotundaria infucata (Conrad, 1834)
- Species Unio infulgens I. Lea, 1874 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio infuscus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio ingallsianus I. Lea, 1852 accepted as Ensidens ingallsianus (I. Lea, 1852)
- Species Unio ingulenzis Gozhik, 1978 †
- Species Unio inornatus Reeve, 1865 accepted as Contradens contradens (I. Lea, 1838)
- Species Unio inornatus I. Lea, 1856 accepted as Lens inornatus (I. Lea, 1856)
- Species Unio inostranzevi Bogachev, 1961 † accepted as Heterunio inostranzevi (Bogachev, 1961) †
- Species Unio insolidus I. Lea, 1872 accepted as Lasmigona decorata (I. Lea, 1852)
- Species Unio instructus I. Lea, 1861 accepted as Pleurobema verum (I. Lea, 1861)
- Species Unio insulsus I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio intercedens I. Lea, 1857 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio intermedia Cornuel, 1874 †
- Species Unio intermedius Conrad, 1836 accepted as Theliderma intermedia (Conrad, 1836)
- Species Unio interruptus Say, 1831 accepted as Plectomerus dombeyanus (Valenciennes, 1827)
- Species Unio interruptus I. Lea, 1838 accepted as Cambarunio taeniatus pictus (I. Lea, 1834)
- Species Unio interventus I. Lea, 1861 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio introrugatus Connolly, 1931 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio inusitatis I. Lea, 1859 accepted as Elliptio hopetonensis (I. Lea, 1838)
- Species Unio invanutus [sic] accepted as Unio invenustus I. Lea, 1874
- Species Unio invenustus I. Lea, 1874 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio involutus Hanley, 1856 accepted as Assamnaia involuta (Hanley, 1856)
- Species Unio ionicus Drouët, 1879
- Species Unio ipsviciensis Etheridge, 1892 † accepted as Mesohyridella ipsviciensis (Etheridge, 1892) †
- Species Unio irgizlaica Lindholm, 1904 accepted as Unio crassus Philipsson, 1788
- Species Unio iridescens Conrad, 1838 accepted as Venustaconcha ellipsiformis (Conrad, 1836)
- Species Unio iridoides C. A. White, 1886 † accepted as Venustaconcha iridoides (C. A. White, 1886) †
- Species Unio irinae (Tolstikova, 1976) †
- Species Unio iris I. Lea, 1829 accepted as Cambarunio iris (I. Lea, 1829)
- Species Unio irrasus I. Lea, 1861 accepted as Pleurobema georgianum (I. Lea, 1841)
- Species Unio irroratus I. Lea, 1827 accepted as Cyprogenia stegaria (Rafinesque, 1820)
- Species Unio irtyshensis Lindholm, 1932 † accepted as Betekeia irtyshensis (Lindholm, 1932) †
- Species Unio irwinensis I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio isfarensis B. I. Chernyshev, 1937 † accepted as Palaeomargaritifera isfarensis (B. I. Chernyshev, 1937) †
- Species Unio istrianus Stossich, 1899 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio jaccardi Locard, 1893 †
- Species Unio jacksoni F. R. Woodward, 1964 †
- Species Unio jacobaeus R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio jaculus Rochebrune, 1882 accepted as Ensidens jaculus (Rochebrune, 1882)
- Species Unio jalpuchae (Gozhik, 2002) †
- Species Unio jamesianus I. Lea, 1857 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio janinae Teisseyre, 1907 † accepted as Cuneopsidea sculpta (Brusina, 1874) †
- Species Unio janschini Bogachev, 1961 † accepted as Potomida janschini (Bogachev, 1961) †
- Species Unio japanensis I. Lea, 1859 accepted as Pronodularia japanensis (I. Lea, 1859)
- Species Unio jaqueti R. B. Newton, 1915 † accepted as Alathyria jaqueti (R. B. Newton, 1915) †
- Species Unio jasamalicus Golubyatnikov, 1927 †
- Species Unio jaspidea Hupé, 1857 accepted as Monocondylaea jaspidea (Hupé, 1857)
- Species Unio jassamalicus [sic] † accepted as Unio jasamalicus Golubyatnikov, 1927 †
- Species Unio jatchevskii Lebedev, 1959 †
- Species Unio jatzkoi Aslanyan, 1970 †
- Species Unio jauberti Locard, 1883 accepted as Unio delicatus I. Lea, 1863
- Species Unio javanus I. Lea, 1840 accepted as Lens contradens (I. Lea, 1838)
- Species Unio jayensis I. Lea, 1838 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio jeffreysianus I. Lea, 1871 accepted as Velesunio ambiguus (R. A. Philippi, 1847)
- Species Unio jejunus I. Lea, 1838 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio jenissejensis Lebedev, 1958 † accepted as Proarcidopsis jenissejensis (Lebedev, 1958) †
- Species Unio jenkinsianus W. H. Benson, 1862 accepted as Lamellidens jenkinsianus (W. H. Benson, 1862)
- Species Unio jensenii Baker accepted as Lasmigona complanata (Barnes, 1823)
- Species Unio jermak Bogachev, 1924 † accepted as Bogatschevia jermak (Bogachev, 1924) †
- Species Unio jewettii I. Lea, 1867 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio jiamudariyaensis (J.-M. Wei, 1984) †
- Species Unio jianchuanensis Q.-H. Ma, 1976 †
- Species Unio jickelii Bourguignat, 1883 accepted as Unio dembeae Reeve, 1865
- Species Unio jirgalitica J.-M. Wei, 1984 †
- Species Unio jiulensis Tournouër, 1880 †
- Species Unio johannis I. Lea, 1859 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio johboehmi Frech, 1911 † accepted as Cuneopsis johboehmi (Frech, 1911) †
- Species Unio johnstoni Etheridge, 1881 † accepted as Prohyria johnstoni (Etheridge, 1881) †
- Species Unio joinvillensis Bourguignat, 1869 †
- Species Unio jokohamensis Ihering, 1894 accepted as Inversiunio jokohamensis (Ihering, 1893)
- Species Unio jonesii I. Lea, 1859 accepted as Cambarunio jonesii (I. Lea, 1859)
- Species Unio jordanicus Bourguignat, 1856 accepted as Unio terminalis Bourguignat, 1852
- Species Unio jordanorum Fontannes, 1884 †
- Species Unio josseti Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio jouberti Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio jourdyi Morlet, 1886 accepted as Nodularia jourdyi (Morlet, 1886)
- Species Unio jovanovici Pavlović, 1931 †
- Species Unio jowikolensis R. B. Newton, 1909 † accepted as Afrohyrioides jowikolensis (R. B. Newton, 1909) †
- Species Unio juliani Rang, 1835 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio jurisici Brusina, 1896 † accepted as Psilunio jurisici (Brusina, 1896) †
- Species Unio kalmykorum Bogachev, 1924 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio karacojunli K. A. Ali-Zade, 1932 †
- Species Unio karakojunli [sic] † accepted as Unio karacojunli K. A. Ali-Zade, 1932 †
- Species Unio karamaica J.-M. Wei, 1984 †
- Species Unio karici Pavlović, 1931 †
- Species Unio karrooensis L. R. Cox, 1932 † accepted as Tihkia karrooensis (L. R. Cox, 1932) †
- Species Unio kasankensis Ragozin, 1954 †
- Species Unio katherinae I. Lea, 1838 accepted as Lasmigona complanata (Barnes, 1823)
- Species Unio katzeri Brusina, 1904 †
- Species Unio kaziaevi Lebedev, 1959 †
- Species Unio keinerianus I. Lea, 1852 accepted as Unio kienerianus I. Lea, 1852
- Species Unio kemensis Lebedev, 1958 †
- Species Unio kendalli J. W. Jackson, 1911 †
- Species Unio kenissara Bogachev, 1924 †
- Species Unio keraudreni Eydoux, 1838 accepted as Indonaia caerulea (I. Lea, 1831)
- Species Unio kettneri Petrbok, 1923 †
- Species Unio keuperinus H. A. C. Berger, 1854 †
- Species Unio khomentovskii Lebedev, 1958 † accepted as Sibirinaia khomentovskii (Lebedev, 1958) †
- Species Unio kienerianus I. Lea, 1852 accepted as Cyclonaias kieneriana (I. Lea, 1852)
- Species Unio kilakuprensis Bogachev, 1936 †
- Species Unio kingii B. H. Wright, 1900 accepted as Medionidus penicillatus (I. Lea, 1857)
- Species Unio kirchbergensis Krauss, 1852 †
- Species Unio kirghisicus Bogachev, 1924 †
- Species Unio kirkii I. Lea, 1864 accepted as Nyassunio nyassaensis (I. Lea, 1864)
- Species Unio kirklandianus S. H. Wright, 1897 accepted as Hamiota subangulata (I. Lea, 1840)
- Species Unio kirnensis Ludwig, 1863 † accepted as Anthracosia kirnensis (Ludwig, 1863) †
- Species Unio kirtlandianus I. Lea, 1834 accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio kisonis Kobelt & Rolle, 1895 accepted as Unio terminalis Bourguignat, 1852
- Species Unio kitzui Cobălcescu, 1883 † accepted as Jazkoa sturzae (Cobălcescu, 1883) †
- Species Unio kizylaigirensis Lindholm, 1932 † accepted as Nodularia kizylaigirensis (Lindholm, 1932) †
- Species Unio kleciaki Drouët, 1879 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio kleinianus I. Lea, 1852 accepted as Rotundaria kleiniana (I. Lea, 1852)
- Species Unio klikai Petrbok, 1923 †
- Species Unio knighti Logan, 1900 †
- Species Unio knightii [sic] † accepted as Unio knighti Logan, 1900 †
- Species Unio kobayasiensis Otuka, 1934 † accepted as Inversidens kobayasiensis (Otuka, 1934) †
- Species Unio kobelti Neumayr, 1899 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio kobelti Kobelt & Rolle, 1895 accepted as Unio delicatus I. Lea, 1863
- Species Unio kochi Kobelt, 1886 accepted as Unio crassus Philipsson, 1788
- Species Unio kohlii Sahni & Bhatnagar, 1957 † accepted as Radiatula kohlii (Sahni & Bhatnagar, 1957) †
- Species Unio korkinensis B. I. Chernyshev, 1937 †
- Species Unio koseritzi Clessin, 1888 accepted as Rhipidodonta koseritzi (Clessin, 1888)
- Species Unio kotschyi Küster, 1862 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio kraussii I. Lea, 1853 accepted as Castaliella sulcata (Krauss, 1849)
- Species Unio kruperi Drouët, 1879 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio ksibianus Mousson, 1874 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio kubekoviensis Lebedev, 1958 † accepted as Tchulymiconcha kubekoviensis (Lebedev, 1958) †
- Species Unio kujalnicensis Mangikian, 1929 †
- Species Unio kukuljevici Brusina, 1878 †
- Species Unio kullethensis I. Lea, 1865 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio kunenensis Mousson, 1888 accepted as Coelatura kunenensis (Mousson, 1888)
- Species Unio kungurensis Kobelt, 1911 accepted as Unio crassus Philipsson, 1788
- Species Unio kusceri Modell, 1940 † accepted as Unio pavlovici pavlovici Brusina, 1902 †
- Species Unio kutschum Bogachev, 1924 † accepted as Rhombuniopsis kutschum (Bogachev, 1924) †
- Species Unio kuweikensis Kobelt, 1912 accepted as Unio delicatus I. Lea, 1863
- Species Unio lacazei Bourguignat, 1881 † accepted as Unio lacazianus Dupuy, 1843 †
- Species Unio lacazi Noulet, 1846 † accepted as Unio lacazianus Dupuy, 1843 †
- Species Unio lacaziana Dupuy, 1843 † accepted as Unio lacazianus Dupuy, 1843 †
- Species Unio lacazianus Dupuy, 1843 †
- Species Unio lacrymosus I. Lea, 1827 accepted as Quadrula quadrula (Rafinesque, 1820)
- Species Unio lacteolus I. Lea, 1834 accepted as Diplodon delodonta (Lamarck, 1819)
- Species Unio laevirostris W. H. Benson, 1862 accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio laevissimus (I. Lea, 1829) accepted as Potamilus ohiensis (Rafinesque, 1820)
- Species Unio lagnisicus Bourguignat, 1882 accepted as Unio mancus Lamarck, 1819
- Species Unio laharpei Locard, 1893 †
- Species Unio lamarckianus I. Lea, 1852 accepted as Cyprogenia aberti (Conrad, 1850)
- Species Unio lamellatus I. Lea, 1838 accepted as Lamellidens lamellatus (I. Lea, 1838)
- Species Unio lampreyanus Baird & H. Adams, 1867 accepted as Schistodesmus lampreyanus (Baird & H. Adams, 1867)
- Species Unio lanceolatiformis J.-S. Yu, 1987 †
- Species Unio lanceolatus I. Lea, 1827 accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio landanensis Schepman, 1891 accepted as Coelatura gabonensis (Küster, 1862)
- Species Unio landbecki R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio languilati Heude, 1874 accepted as Lepidodesma languilati (Heude, 1874)
- Species Unio laosensis I. Lea, 1863 accepted as Gibbosula laosensis (I. Lea, 1863)
- Species Unio lapidosus Kobelt, 1893 accepted as Lampsilis discus (I. Lea, 1838)
- Species Unio lapilloides C. A. White, 1886 † accepted as Medionidus lapilloides (C. A. White, 1886) †
- Species Unio lapillus Say, 1831 accepted as Unio capillus Say, 1831
- Species Unio lapparenti Mongin, 1963 † accepted as Rostrunio lapparenti (Mongin, 1963) †
- Species Unio largillierti R. A. Philippi, 1847 accepted as Delphinonaias largillierti (R. A. Philippi, 1847)
- Species Unio larius Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio larteti Noulet, 1846 † accepted as Elliptio larteti (Noulet, 1846) †
- Species Unio latecostatus I. Lea, 1845 accepted as Amblema plicata (Say, 1817)
- Species Unio lateralis (T. Brown, 1843) † accepted as Anthracosia lateralis (T. Brown, 1843) †
- Species Unio laticeps E. von Martens, 1900 accepted as Lens contradens (I. Lea, 1838)
- Species Unio latiplicatus Noulet, 1864 † accepted as Margaritifera (Pseudunio) flabellata (Goldfuss, 1837) †
- Species Unio latiradiatus Conrad, 1838 accepted as Cambarunio taeniatus pictus (I. Lea, 1834)
- Species Unio latirostris Küster, 1853 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio latissimus G. B. Sowerby II, 1868 accepted as Lampsilis cardium Rafinesque, 1820
- Species Unio latus I. Lea, 1859 accepted as Elliptio roanokensis (I. Lea, 1838)
- Species Unio lauterborni F. Haas, 1909 accepted as Unio tumidus Philipsson, 1788
- Species Unio lavateri Münster, 1837 † accepted as Anodonta lavateri (Münster, 1837) †
- Species Unio lavigerianus Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio lawii I. Lea, 1871 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio layardii I. Lea, 1859 accepted as Lamellidens lamellatus (I. Lea, 1838)
- Species Unio laymontianus Noulet, 1846 †
- Species Unio lazarus I. Lea, 1852 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio leaii J. E. Gray, 1833 accepted as Lamprotula leaii (J. E. Gray, 1833)
- Species Unio leanus Meek, 1871 †
- Species Unio lechaptoisi Ancey, 1894 accepted as Coelatura mossambicensis (E. von Martens, 1860)
- Species Unio lecontianus I. Lea, 1838 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio ledoulxianus Charmes, 1885 accepted as Coelatura ratidota (Charmes, 1885)
- Species Unio leei Z.-M. Zhang, 1976 †
- Species Unio legrandi Petterd, 1889 accepted as Velesunio moretonicus (Reeve, 1865)
- Species Unio lehmanii S. H. Wright, 1897 accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio leibii I. Lea, 1862 accepted as Obovaria subrotunda Rafinesque, 1820
- Species Unio leioma W. H. Benson, 1862 accepted as Indonaia bonneaudii (Eydoux, 1838)
- Species Unio lenior I. Lea, 1842 accepted as Epioblasma lenior (I. Lea, 1842)
- Species Unio lenis I. Lea, 1840 accepted as Unio lenior I. Lea, 1842
- Species Unio lenis Conrad, 1838 accepted as Lampsilis cardium Rafinesque, 1820
- Species Unio lens I. Lea, 1831 accepted as Obovaria subrotunda Rafinesque, 1820
- Species Unio lenticularis I. Lea, 1872 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio lenticularis Stefanescu, 1896 † accepted as Rugunio lenticularis (Stefanescu, 1896) †
- Species Unio leonensis C. T. Simpson, 1892 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio leopoldvillensis Putzeys, 1899 accepted as Coelatura leopoldvillensis (Putzeys, 1899)
- Species Unio lepidus A. Gould, 1856 accepted as Villosa amygdalum (I. Lea, 1843)
- Species Unio lepidus I. Lea, 1860 accepted as Margaron lepidior I. Lea, 1870
- Species Unio lepidus Ludwig, 1861 † accepted as Anthraconaia carbonaria (Schlotheim, 1820) †
- Species Unio leprosus Miles, 1861 accepted as Ligumia recta (Lamarck, 1819)
- Species Unio lesleyi I. Lea, 1860 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio lessoni Küster, 1855 accepted as Hyridella australis (Lamarck, 1819)
- Species Unio lesueurianus I. Lea, 1840 accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio letsoni Whitfield, 1907 † accepted as Proparreysia letsoni (Whitfield, 1907) †
- Species Unio levanticus Halaváts, 1914 †
- Species Unio levedensis (T. Brown, 1843) † accepted as Carbonicola acuta (J. Sowerby, 1813) †
- Species Unio lewisii I. Lea, 1861 accepted as Pleurobema fibuloides (I. Lea, 1859)
- Species Unio lianggaoshanensis X.-Z. Liu, 1984 †
- Species Unio liangshanensis X.-Z. Liu, 1988 †
- Species Unio liasinus Zieten, 1833 † accepted as Panopaea liasina (Zieten, 1833) †
- Species Unio liebmanni R. A. Philippi, 1847 accepted as Sphenonaias liebmanni (R. A. Philippi, 1847)
- Species Unio liederi E. von Martens, 1897 accepted as Coelatura mossambicensis (E. von Martens, 1860)
- Species Unio liedtkei Rolle, 1904 accepted as Aculamprotula nodulosa (W. Wood, 1815)
- Species Unio lienosus Conrad, 1834 accepted as Leaunio lienosus (Conrad, 1834)
- Species Unio ligamentina Lamarck, 1819 accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio ligamentinoides I. Lea, 1868 † accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio ligatus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio lignitarius Rolle, 1858 †
- Species Unio ligula Mousson, 1849 accepted as Lamellidens marginalis (Lamarck, 1819)
- Species Unio lijacensis Kobelt, 1890 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio limatulus Conrad, 1849 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio limensis Küster, 1856 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio limosus Nilsson, 1822 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio lincecumii I. Lea, 1868 accepted as Amblema plicata (Say, 1817)
- Species Unio lindholmi Zhadin, 1938 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio lindsleyi I. Lea, 1860 accepted as Villosa taeniata (Conrad, 1834)
- Species Unio lineata Bory de St. Vincent, 1827 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio lineatus I. Lea, 1840 accepted as Lampsilis binominata C. T. Simpson, 1900
- Species Unio lineolatus (Rafinesque, 1820) accepted as Ellipsaria lineolata (Rafinesque, 1820)
- Species Unio linguaeformis I. Lea, 1860 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio linguiformis J. Phillips, 1839 †
- Species Unio lingulatus Drouët & Chaper, 1892 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio lintneri Milošević, 1968 †
- Species Unio listeri J. Sowerby, 1817 † accepted as Cardinia listeri (J. Sowerby, 1817) †
- Species Unio literatus Bielz, 1864 †
- Species Unio littoralis Cuvier, 1798 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio litus I. Lea, 1871 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio livingstonensis I. Lea, 1863 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio locellus I. Lea, 1866 accepted as Rhipidodonta variabilis (Maton, 1811)
- Species Unio lombardi Kow. †
- Species Unio longedentatus Anton, 1838
- Species Unio longirostris Rossmässler, 1836 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio longobardus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio longus (G.-X. Zhu, 1976) †
- Species Unio longus R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio lorioli Locard, 1893 †
- Species Unio lorteti Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio lottneri Ludwig, 1861 † accepted as Carbonicola acuta (J. Sowerby, 1813) †
- Species Unio lourdeli Bourguignat, 1887 accepted as Nitia monceti (Bourguignat, 1883)
- Species Unio lucaogouensis J.-M. Wei, 1984 †
- Species Unio lucidus I. Lea, 1863 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio lufengensis Q.-H. Ma, 1974 † accepted as Pseudunio lufengensis (Q.-H. Ma, 1974) †
- Species Unio lugens Drouët & Chaper, 1892 accepted as Lens lugens (Drouët & Chaper, 1892)
- Species Unio lugubris I. Lea, 1838 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio lugubris Say, 1832 accepted as Potamilus purpuratus (Lamarck, 1819)
- Species Unio lukovici Pavlović, 1931 †
- Species Unio lunae Voitești, 1927 † accepted as Parvidacna lunae (Voitești, 1927) †
- Species Unio lunulatus W. H. Pratt, 1876 accepted as Quadrula quadrula (Rafinesque, 1820)
- Species Unio lunulifer Bourguignat, 1856 accepted as Unio terminalis Bourguignat, 1852
- Species Unio luochengensis X.-Z. Liu & G.-X. Zhu, 1978 †
- Species Unio luridus I. Lea, 1852 accepted as Elliptio arca (Conrad, 1834)
- Species Unio lutens I. Lea, 1856 accepted as Unio luteus I. Lea, 1856
- Species Unio luteola Lamarck, 1819 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio luteolus Lamarck, 1819 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio luteus I. Lea, 1856 accepted as Leoparreysia tavoyensis (A. Gould, 1843)
- Species Unio lutulentus A. Gould, 1850 accepted as Echyridella menziesii (J. E. Gray, 1843)
- Species Unio luxurians Küster, 1854 accepted as Unio crassus Philipsson, 1788
- Species Unio luynesi Locard, 1883 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio lycicus Kobelt & Rolle, 1895 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio lyonii I. Lea, 1865 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio macer I. Lea, 1857 accepted as Elliptio roanokensis (I. Lea, 1838)
- Species Unio macilentus W. H. Benson, 1862 accepted as Indonaia gratiosa (R. A. Philippi, 1843)
- Species Unio macnielii I. Lea, 1869 accepted as Nephronaias macnielii (I. Lea, 1869)
- Species Unio maconensis I. Lea, 1857 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio macrodon I. Lea, 1859 accepted as Truncilla macrodon (I. Lea, 1859)
- Species Unio macropisthus C. A. White, 1886 †
- Species Unio macropterus Dunker, 1846 accepted as Physunio superbus (I. Lea, 1843)
- Species Unio mactraeformis Brusina, 1902 † accepted as Sinanodonta mactraeformis (Brusina, 1902) †
- Species Unio mactraeformis Ionescu-Argetoaia, 1918 † accepted as Potomida mactraeformis (Ionescu-Argetoaia, 1918) †
- Species Unio mactrella Bogachev, 1908 †
- Species Unio maculatus Conrad, 1834 accepted as Pleuronaia dolabelloides (I. Lea, 1840)
- Species Unio madagascariensis Sganzin, 1841 accepted as Coelatura madagascariensis (Sganzin, 1841)
- Species Unio maestus I. Lea, 1841 accepted as Toxolasma lividum Rafinesque, 1831
- Species Unio magistri Westerlund, 1890 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio malcolmensis [sic] † accepted as Unio malcolmsoni Hislop, 1860 †
- Species Unio malcolmsoni Hislop, 1860 † accepted as Parreysia subtumida (A. d'Orbigny, 1850) †
- Species Unio malgachensis Germain, 1911 accepted as Coelatura malgachensis (Germain, 1911)
- Species Unio maltzani Küster, 1854 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio mamillatus Hislop, 1860 † accepted as Parreysia mamillata (Hislop, 1860) †
- Species Unio mammillaris Yen, 1952 † accepted as Vetulonaia mammillaris (Yen, 1952) †
- Species Unio manasensis J.-M. Wei, 1984 † accepted as Palaeomargaritifera manasensis (J.-M. Wei, 1984) †
- Species Unio manca Lamarck, 1819 accepted as Unio mancus Lamarck, 1819
- Species Unio mancus Lamarck, 1819
- Species Unio mandarinus Morelet, 1864 accepted as Scabies mandarinus (Morelet, 1864)
- Species Unio mandelayensis Theobald, 1873 accepted as Leoparreysia bhamoensis (Theobald, 1873)
- Species Unio mandelslohi Dunker, 1848 †
- Species Unio mandinguorum Rochebrune, 1882 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio mangikiani Jatsko, 1954 † accepted as Betekeia mangikiani (Jatsko, 1954) †
- Species Unio mantellii J. De C. Sowerby, 1836 †
- Species Unio manubius A. Gould, 1855 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio mardinensis I. Lea, 1865
- Species Unio margaritifer (Linnaeus, 1758) accepted as Margaritifera (Margaritifera) margaritifera (Linnaeus, 1758)
- Species Unio margaritifera (Linnaeus, 1758) accepted as Margaritifera margaritifera (Linnaeus, 1758)
- Species Unio marginalis Lamarck, 1819 accepted as Lamellidens marginalis (Lamarck, 1819)
- Species Unio marginis I. Lea, 1865 accepted as Toxolasma paulum (I. Lea, 1840)
- Species Unio marshii B. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio marteli Pallary, 1918 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio martensi Ihering, 1893 accepted as Diplodon martensi (Ihering, 1893)
- Species Unio martinii J. De C. Sowerby, 1836 †
- Species Unio martinovae [sic] † accepted as Unio martynovae Martinson & Hong, 1961 †
- Species Unio martynovae Martinson & Hong, 1961 †
- Species Unio mashonae Preston, 1910 accepted as Cafferia caffra (Krauss, 1848)
- Species Unio maslakovetzianus Bogachev, 1924 †
- Species Unio masoni Conrad, 1834 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio massini Morelet, 1864 accepted as Physunio massini (Morelet, 1864)
- Species Unio mastodontophila Sacco, 1889 †
- Species Unio mastodontophylus [sic] † accepted as Unio mastodontophila Sacco, 1889 †
- Species Unio matoniana A. d'Orbigny, 1835 accepted as Rhipidodonta variabilis (Maton, 1811)
- Species Unio matyasovskyi Halaváts, 1902 †
- Species Unio mauritianus I. Lea, 1859 accepted as Simpsonella purpurea (Valenciennes, 1827)
- Species Unio maximus T. Fuchs, 1870 † accepted as Limnoscapha (Limnoscapha) maxima (T. Fuchs, 1870) †
- Species Unio mayeri Choffat, 1885 †
- Species Unio mclearni Dyer, 1930 † accepted as Proparreysia mclearni (Dyer, 1930) †
- Species Unio mecklenbergensis I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio medellinus I. Lea, 1838 accepted as Actinonaias medellina (I. Lea, 1838)
- Species Unio mederianus Küster, 1861 accepted as Lens contradens (I. Lea, 1838)
- Species Unio medicus Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio mediocris I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio medius I. Lea, 1861 accepted as Pleurobema georgianum (I. Lea, 1841)
- Species Unio medjerdae Kobelt, 1884 accepted as Unio ravoisieri Deshayes, 1848
- Species Unio medulici Brusina, 1902 † accepted as Potomida medulici (Brusina, 1902) †
- Species Unio meeki C. A. White, 1877 † accepted as Unio leanus Meek, 1871 †
- Species Unio megapterus Morelet, 1864 accepted as Hyriopsis bialata C. T. Simpson, 1900
- Species Unio melinus Conrad, 1838 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio melleus I. Lea, 1859 accepted as Nephronaias mellea (I. Lea, 1859)
- Species Unio menardi Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio mendax C. A. White, 1877 † accepted as Plesielliptio mendax (C. A. White, 1877) †
- Species Unio meneliki Bourguignat, 1885 accepted as Unio dembeae Reeve, 1865
- Species Unio mengrelicus Drouët, 1881 accepted as Unio crassus Philipsson, 1788
- Species Unio menkei F. C. L. Koch & Dunker, 1837 † accepted as Margaritifera menkei (F. C. L. Koch & Dunker, 1837) †
- Species Unio menkianus I. Lea, 1838 accepted as Cambarunio taeniatus pictus (I. Lea, 1834)
- Species Unio menziesii J. E. Gray, 1843 accepted as Echyridella menziesii (J. E. Gray, 1843)
- Species Unio mercerii I. Lea, 1862 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio meredithii I. Lea, 1858 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio merodabensis Küster, 1861 accepted as Parreysia nagpoorensis (I. Lea, 1860)
- Species Unio merus I. Lea, 1852 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio mesaverdensis Yen, 1954 †
- Species Unio messageri Bavay & Dautzenberg, 1901 accepted as Protunio messageri (Bavay & Dautzenberg, 1901)
- Species Unio metallicus Say, 1831 accepted as Popenaias metallica (Say, 1831)
- Species Unio metanevra (Rafinesque, 1820) accepted as Theliderma metanevra (Rafinesque, 1820)
- Species Unio metastriatus Conrad, 1838 accepted as Epioblasma metastriata (Conrad, 1838)
- Species Unio metohiensis Milošević, 1968 †
- Species Unio mexicanus R. A. Philippi, 1847 accepted as Sphenonaias mexicana (R. A. Philippi, 1847)
- Species Unio micans I. Lea, 1857 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio micelii Kobelt, 1884 accepted as Unio ravoisieri Deshayes, 1848
- Species Unio michaudi Deshayes, 1858 † accepted as Propotomida michaudi (Deshayes, 1858) †
- Species Unio micheloti Morlet, 1886 accepted as Nodularia micheloti (Morlet, 1886)
- Species Unio michonii Bourguignat, 1852 accepted as Leguminaia saulcyi (Bourguignat, 1852)
- Species Unio microdon E. von Martens, 1887 accepted as Sphenonaias microdon (E. von Martens, 1887)
- Species Unio micropterus Morelet, 1866 accepted as Lens micropterus (Morelet, 1866)
- Species Unio microstictus Heude, 1877 accepted as Lamprotula microsticta (Heude, 1877)
- Species Unio middendorffi Westerlund, 1890 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio migliorinii Magrograssi, 1928 †
- Species Unio mihanovici Brusina, 1896 †
- Species Unio mikhailovskii Bogachev, 1961 †
- Species Unio mingrelicus accepted as Unio crassus Philipsson, 1788
- Species Unio minimus P. S. Warren, 1926 † accepted as Fusconaia stantoni (C. A. White, 1907) †
- Species Unio minor I. Lea, 1843 accepted as Toxolasma paulum (I. Lea, 1840)
- Species Unio minusculus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio minusculus Repman, 1963 †
- Species Unio minutus J.-S. Yu, 1987 †
- Species Unio miquanensis J.-M. Wei, 1984 †
- Species Unio mirabilis J.-S. Yu, 1980 †
- Species Unio miribellensis Locard, 1883 † accepted as Unio venerius Fontannes, 1880 †
- Species Unio misellus Morelet, 1865 accepted as Lens misellus (Morelet, 1865)
- Species Unio misoolensis Schepman, 1897 accepted as Hyridella misoolensis (Schepman, 1897)
- Species Unio mississippiensis Conrad, 1849 accepted as Ligumia subrostrata (Say, 1831)
- Species Unio mitchelli C. T. Simpson, 1895 accepted as Fusconaia mitchelli (C. T. Simpson, 1895)
- Species Unio modelli Moisescu, 1968 †
- Species Unio modestus Küster, 1856 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio modicellus I. Lea, 1859 accepted as Epioblasma othcaloogensis (I. Lea, 1857)
- Species Unio modicus I. Lea, 1857 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio modiola Preston, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio modiolaris J. De C. Sowerby, 1840 † accepted as Anthraconaia modiolaris (J. De C. Sowerby, 1840) †
- Species Unio modioliformis I. Lea, 1834 accepted as Villosa vibex (Conrad, 1834)
- Species Unio moineti Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio mojsvari Penecke, 1883 † accepted as Rugunio mojsvari (Penecke, 1883) †
- Species Unio moldavicus (Stefanescu, 1896) †
- Species Unio moldaviensis M. Hörnes, 1864 † accepted as Rugunio moldaviensis (M. Hörnes, 1864) †
- Species Unio molinae R. A. Philippi, 1847 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio molleuri Morlet, 1891 accepted as Unionetta fabagina (Deshayes, 1876)
- Species Unio monceti Bourguignat, 1883 accepted as Nitia monceti (Bourguignat, 1883)
- Species Unio mongolicus Middendorff, 1850 accepted as Middendorffinaia mongolica (Middendorff, 1850)
- Species Unio monodonta Say, 1829 accepted as Margaritifera monodonta (Say, 1829)
- Species Unio monroensis I. Lea, 1843 accepted as Elliptio monroensis (I. Lea, 1843)
- Species Unio montanus R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio mooresianus I. Lea, 1857 accepted as Pleuronaia dolabelloides (I. Lea, 1840)
- Species Unio moraiensis K. Suzuki, 1941 † accepted as Calyptogena pacifica Dall, 1891
- Species Unio moravicus M. Hörnes, 1864 †
- Species Unio moreniensis Botez, 1914 † accepted as Psilunio moreniensis (Botez, 1914) †
- Species Unio moretonicus Reeve, 1865 accepted as Velesunio moretonicus (Reeve, 1865)
- Species Unio morini Morelet, 1851
- Species Unio morlachicus Kobelt, 1914 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio morovici Brusina, 1878 † accepted as Potomida clivosa (Brusina, 1874) †
- Species Unio mortoni Conrad, 1835 accepted as Cyclonaias mortoni (Conrad, 1835)
- Species Unio moskoni Papaianopol, 1989 †
- Species Unio mossambicensis E. von Martens, 1860 accepted as Coelatura mossambicensis (E. von Martens, 1860)
- Species Unio mosulensis I. Lea, 1863 accepted as Unio tigridis Bourguignat, 1852
- Species Unio moussonianus I. Lea, 1852 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio mrazeci Ionescu-Argetoaia, 1918 † accepted as Pristinunio mrazeci (Ionescu-Argetoaia, 1918) †
- Species Unio mucidus Morelet, 1845 accepted as Unio delphinus Spengler, 1793
- Species Unio mucronatus Barnes, 1823 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio muelleri Rossmässler, 1838 accepted as Unio tumidus Philipsson, 1788
- Species Unio muenzenbergensis Ludwig, 1861 †
- Species Unio mugodjaricus Bogachev, 1961 † accepted as Nodularia mugodjarica (Bogachev, 1961) †
- Species Unio muhlfeldianus I. Lea, 1838 accepted as Cambarunio dactylus dactylus (I. Lea, 1840)
- Species Unio multicolor E. von Martens, 1897 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio multidentatus R. A. Philippi, 1847 accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio multiplicatus I. Lea, 1831 accepted as Megalonaias nervosa (Rafinesque, 1820)
- Species Unio multiradiatus I. Lea, 1829 accepted as Lampsilis fasciola Rafinesque, 1820
- Species Unio multistriatus I. Lea, 1831 accepted as Diplodon multistriatus (I. Lea, 1831)
- Species Unio mundus I. Lea, 1857 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio munteniae Teisseyre, 1907 †
- Species Unio murchinsonianus I. Lea, 1834 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio murinum Heude, 1883 accepted as Ptychorhynchus murinum (Heude, 1883)
- Species Unio murrayensis I. Lea, 1868 accepted as Pleurobema stabilis (I. Lea, 1861)
- Species Unio mushketovi Martinson, 1965 †
- Species Unio musius Dall, 1913 †
- Species Unio musivus Spengler, 1793 accepted as Unio crassus Philipsson, 1788
- Species Unio mussolianus Küster, 1861 accepted as Unio tigridis Bourguignat, 1852
- Species Unio mutabilis I. Lea, 1859 accepted as Hyridella depressa (Lamarck, 1819)
- Species Unio mutatus Mousson, 1849 accepted as Lens contradens (I. Lea, 1838)
- Species Unio mutelaeformis Germain, 1907 accepted as Nitia mutelaeformis (Germain, 1907)
- Species Unio mweruensis E. A. Smith, 1908 accepted as Prisodontopsis mweruensis (E. A. Smith, 1908)
- Species Unio myersianus I. Lea, 1856 accepted as Hyriopsis myersiana (I. Lea, 1856)
- Species Unio mysticus Pallary, 1902 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio mytiloides (Rafinesque, 1820) accepted as Pleurobema clava (Lamarck, 1819)
- Species Unio naftalanicus K. A. Ali-Zade, 1932 †
- Species Unio nagnomensis Hoffet, 1937 † accepted as Pseudohyria nagnomensis (Hoffet, 1937) †
- Species Unio nagpoorensis I. Lea, 1860 accepted as Parreysia nagpoorensis (I. Lea, 1860)
- Species Unio nairica Aslanyan, 1970 † accepted as Unio nairicus Aslanyan, 1970 †
- Species Unio nairicus Aslanyan, 1970 †
- Species Unio nana Lamarck, 1819 accepted as Unio nanus Lamarck, 1819
- Species Unio nanaimoensis Whiteaves, 1901 † accepted as Elliptio nanaimoensis (Whiteaves, 1901) †
- Species Unio nansensis "Matheron" †
- Species Unio nanus Lamarck, 1819
- Species Unio nanxiensis X.-Z. Liu, 1984 †
- Species Unio naphtalanicus [sic] † accepted as Unio naftalanicus K. A. Ali-Zade, 1932 †
- Species Unio nardoi Brusina, 1902 † accepted as Potomida zelebori (M. Hörnes, 1864) †
- Species Unio nashvillianus I. Lea, 1834 accepted as Ligumia subrostrata (Say, 1831)
- Species Unio nasuta Lamarck, 1819 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio nasutidus I. Lea, 1863 accepted as Elliptio producta (Conrad, 1836)
- Species Unio nasutilus [sic] accepted as Unio nasutidus I. Lea, 1863
- Species Unio nasutoides I. Lea, 1868 † accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio nasutulus "Lea" accepted as Unio nasutidus I. Lea, 1863
- Species Unio nasutus Say, 1817 accepted as Sagittunio nasutus (Say, 1817)
- Species Unio natolicus Küster, 1856 accepted as Unio tigridis Bourguignat, 1852
- Species Unio natosini McLearn, 1929 † accepted as Quadrula natosini (McLearn, 1929) †
- Species Unio naviculoides I. Lea, 1857 accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio naviformis Lamarck, 1819 accepted as Theliderma cylindrica (Say, 1817)
- Species Unio navigioliformis I. Lea, 1859 accepted as Cucumerunio novaehollandiae (Gray, 1834)
- Species Unio nebulosus Conrad, 1834 accepted as Villosa nebulosa (Conrad, 1834)
- Species Unio negatus I. Lea, 1861 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio neglectus I. Lea, 1843 accepted as Lasmigona subviridis (Conrad, 1835)
- Species Unio negreli Fabre-Taxy, 1951 †
- Species Unio neislerii I. Lea, 1858 accepted as Amblema neislerii (I. Lea, 1858)
- Species Unio neocomensis Drouët, 1881 accepted as Unio crassus Philipsson, 1788
- Species Unio neomexicanus Stanton, 1916 † accepted as Pleuronaia neomexicana (Stanton, 1916) †
- Species Unio nepeanensis Conrad, 1850 accepted as Hyridella australis (Lamarck, 1819)
- Species Unio nessorhynchus Küster, 1854 accepted as Unio crassus Philipsson, 1788
- Species Unio neszmelyensis Halaváts, 1923 † accepted as Psilunio jurisici (Brusina, 1896) †
- Species Unio neumayri Brusina, 1878 † accepted as Cuneopsidea oriovacensis (M. Hörnes, 1864) †
- Species Unio neumayri Penecke, 1883 † accepted as Psilunio jurisici (Brusina, 1896) †
- Species Unio neusensis I. Lea, 1858 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio neustruevi Andrusov, 1906 † accepted as Ebersininaia neustruevi (Andrusov, 1906) †
- Species Unio newcombianus I. Lea, 1856 accepted as Arotonaias cyrenoides (R. A. Philippi, 1847)
- Species Unio newcombii "I. Lea" accepted as Unio newcombianus I. Lea, 1856
- Species Unio nexus Say, 1831 accepted as Epioblasma arcaeformis (I. Lea, 1831)
- Species Unio ngesianus E. von Martens, 1897 accepted as Coelatura stuhlmanni (E. von Martens, 1897)
- Species Unio nicaraguensis I. Lea, 1868 accepted as Arotonaias gabbianus (I. Lea, 1868)
- Species Unio nicklinianus I. Lea, 1834 accepted as Megalonaias nickliniana (I. Lea, 1834)
- Species Unio nicolaianus Brusina, 1874 †
- Species Unio nicolasi Fontannes, 1883 † accepted as Potomida nicolasi (Fontannes, 1883) †
- Species Unio nicopolis Jatsko, 1955 †
- Species Unio nieuwenhuisi Schepman, 1898 accepted as Schepmania nieuwenhuisi (Schepman, 1898)
- Species Unio nigellus I. Lea, 1852 accepted as Elliptio nigella (I. Lea, 1852)
- Species Unio nigerrimus I. Lea, 1852 accepted as Leaunio lienosus caliginosus (I. Lea, 1845)
- Species Unio nigrinus I. Lea, 1852 accepted as Villosa vibex (Conrad, 1834)
- Species Unio niloticus Cailliaud, 1823 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio nilssoni F. C. L. Koch & Dunker, 1837 † accepted as Cardinia nilssoni (F. C. L. Koch & Dunker, 1837) †
- Species Unio ningxiaensis Hua, 1965 †
- Species Unio nipponensis E. von Martens, 1877 accepted as Nodularia nipponensis (E. von Martens, 1877)
- Species Unio nitens I. Lea, 1840 accepted as Villosa vanuxemensis (I. Lea, 1838)
- Species Unio nitidosus Drouët, 1879 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio nitidus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio njemcici Brusina, 1902 † accepted as Psilunio jurisici (Brusina, 1896) †
- Species Unio nobilis Conrad, 1854 accepted as Quadrula nobilis (Conrad, 1854)
- Species Unio nocturnis I. Lea, 1860 accepted as Unio nocturnus I. Lea, 1860
- Species Unio nocturnus I. Lea, 1860 accepted as Rhipidodonta funebralis (I. Lea, 1860)
- Species Unio nodiferus Conrad, 1841 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio nodosa Swainson, 1840 accepted as Aculamprotula nodulosa (W. Wood, 1815)
- Species Unio nodosus Barnes, 1823 accepted as Theliderma metanevra (Rafinesque, 1820)
- Species Unio nolani B. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio northamptonensis I. Lea, 1862 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio notatus I. Lea, 1838 accepted as Cambarunio simus (I. Lea, 1838)
- Species Unio novaehollandiae Gray, 1834 accepted as Cucumerunio novaehollandiae (Gray, 1834)
- Species Unio novieboraci I. Lea, 1838 accepted as Villosa iris (I. Lea, 1829)
- Species Unio novorossicus Sinzov, 1897 † accepted as Psilunio novorossicus (Sinzov, 1897) †
- Species Unio novskaensis Penecke, 1883 † accepted as Potomida slavonica (M. Hörnes, 1864) †
- Species Unio nubianus L. R. Cox, 1955 †
- Species Unio nubilus I. Lea, 1868 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio nucalis Meek & Hayden, 1858 † accepted as Glebula nucalis (Meek & Hayden, 1858) †
- Species Unio nucleopsis Conrad, 1849 accepted as Pleurobema georgianum (I. Lea, 1841)
- Species Unio nucleus I. Lea, 1856 accepted as Scabies nucleus (I. Lea, 1856)
- Species Unio nucleus (T. Brown, 1843) † accepted as Pachyodon nucleus T. Brown, 1843 †
- Species Unio nuculinus R. A. Philippi, 1849 accepted as Micronaias arata (I. Lea, 1843)
- Species Unio numantinus Palacios & R. Sánchez, 1885 † accepted as Protopleurobema numantina (Palacios & R. Sánchez, 1885) †
- Species Unio nurensis (Tolstikova, 1976) †
- Species Unio nuttalli F. R. Woodward, 1965 †
- Species Unio nuttallianus I. Lea, 1856 accepted as Indonaia caerulea (I. Lea, 1831)
- Species Unio nux I. Lea, 1852 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio nuxpersicae Dunker, 1849 accepted as Nodularia nuxpersicae (Dunker, 1848)
- Species Unio nyassae G. B. Sowerby II, 1866
- Species Unio nyassaensis I. Lea, 1864 accepted as Nyassunio nyassaensis (I. Lea, 1864)
- Species Unio obesus I. Lea, 1831 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio obfuscus I. Lea, 1857 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio oblatus C. T. Simpson, 1914 accepted as Unio ablatus I. Lea, 1863
- Species Unio obliqua Lamarck, 1819 accepted as Pleurobema cordatum (Rafinesque, 1820)
- Species Unio obliquiradiatus Reeve, 1865 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio oblitus I. Lea, 1870 accepted as Scabies scobinatus (I. Lea, 1856)
- Species Unio oblongus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio obnubilus I. Lea, 1857 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio obrutschewi Martinson, 1956 †
- Species Unio obscurus I. Lea, 1838 accepted as Leaunio vanuxemensis (I. Lea, 1838)
- Species Unio obtusa A. d'Orbigny, 1835 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio obtusus I. Lea, 1840 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio obtusus Ludwig, 1860 †
- Species Unio obuncus I. Lea, 1871 accepted as Fusconaia cor (Conrad, 1834)
- Species Unio occatus I. Lea, 1860 accepted as Indonaia gratiosa (R. A. Philippi, 1843)
- Species Unio occidens I. Lea, 1829 accepted as Lampsilis cardium Rafinesque, 1820
- Species Unio occidentalis Conrad, 1836 accepted as Ptychobranchus occidentalis (Conrad, 1836)
- Species Unio occultus I. Lea, 1843 accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio ochmulgensis accepted as Unio ocmulgeensis I. Lea, 1861
- Species Unio ochraceus Say, 1817 accepted as Atlanticoncha ochracea (Say, 1817)
- Species Unio ocmulgeensis I. Lea, 1861 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio odessanus Jatsko, 1954 †
- Species Unio ogamigoensis T. Kobayashi & K. Suzuki, 1937 †
- Species Unio ogeecheensis Conrad, 1849 accepted as Villosa delumbis (Conrad, 1834)
- Species Unio ogerieni Locard, 1883 † accepted as Unio atavus M. Hörnes, 1864 †
- Species Unio olivarius I. Lea, 1831 accepted as Indonaia olivaria (I. Lea, 1831)
- Species Unio omiensis Heimburg, 1884 accepted as Obovalis omiensis (Heimburg, 1884)
- Species Unio onariotis C. Mayer, 1869 † accepted as Plesielliptio onariotis (C. Mayer, 1869) †
- Species Unio opacatus Crosse & P. Fischer, 1894 accepted as Barynaias opacata (Crosse & P. Fischer, 1894)
- Species Unio opacus I. Lea, 1857 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio opalinus J. G. Anthony, 1866 accepted as Villosa iris (I. Lea, 1829)
- Species Unio opisodartos Adami, 1882 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio opperti Bourguignat, 1856 accepted as Pseudodontopsis euphratica (Bourguignat, 1852)
- Species Unio orachovacensis [sic] † accepted as Unio orahovacensis Milošević, 1968 †
- Species Unio orahovacensis Milošević, 1968 †
- Species Unio oratus Conrad, 1849 accepted as Lampsilis cariosa (Say, 1817)
- Species Unio orbiculatus Hildreth, 1828 accepted as Obovaria subrotunda Rafinesque, 1820
- Species Unio orbignyana Hupé, 1857 accepted as Castalia orbignyi (Deville & Hupé, 1850)
- Species Unio orbignyi Deville & Hupé, 1850 accepted as Castalia orbignyi (Deville & Hupé, 1850)
- Species Unio orcuttii S. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio oregonensis I. Lea, 1852 accepted as Nephronaias oregonensis (I. Lea, 1852)
- Species Unio orescui Cobălcescu, 1883 †
- Species Unio oriens I. Lea, 1831 accepted as Hemistena lata (Rafinesque, 1820)
- Species Unio oriensis Bogachev, 1961 † accepted as Potomida oriensis (Bogachev, 1961) †
- Species Unio orientalis I. Lea, 1840 accepted as Elongaria orientalis (I. Lea, 1840)
- Species Unio orientalis Bourguignat, 1852 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio oriovacensis M. Hörnes, 1864 † accepted as Cuneopsidea oriovacensis (M. Hörnes, 1864) †
- Species Unio orlovi Lindholm, 1932 † accepted as Acuticosta orlovi (Lindholm, 1932) †
- Species Unio ornatus I. Lea, 1861 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio orontesensis I. Lea, 1863 accepted as Unio damascensis I. Lea, 1863
- Species Unio orphaensis I. Lea, 1865 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio ortonii I. Lea, 1868 accepted as Prisodon obliquus Schumacher, 1817
- Species Unio osadtschenkoae Jatsko, 1954 †
- Species Unio osbeckii R. A. Philippi, 1844 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio oscari B. H. Wright, 1892 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio oslavanensis Rzehak, 1893 † accepted as Unio lavateri Münster, 1837 †
- Species Unio ostiorum Servain, 1886 accepted as Unio crassus Philipsson, 1788
- Species Unio ostreatus Morelet, 1849 accepted as Psoronaias ostreata (Morelet, 1849)
- Species Unio otcaloogensis "I. Lea, 1857" accepted as Epioblasma othcaloogensis (I. Lea, 1857)
- Species Unio othcaloogensis I. Lea, 1857 accepted as Epioblasma othcaloogensis (I. Lea, 1857)
- Species Unio ottiliae Penecke, 1883 † accepted as Psilunio (Psilunio) ottiliae (Penecke, 1883) †
- Species Unio ovalis (Montagu, 1803) accepted as Unio tumidus Philipsson, 1788
- Species Unio ovalis C. M. Kolesnikov, 1956 † accepted as Unio colensis Martinson, 1961 †
- Species Unio ovatus Y.-Y. Liu, Y.-H. Duan & Y.-X. Wang, 1994 accepted as Ptychorhynchus liuovatus (He & Zhuang, 2013)
- Species Unio ovatus Say, 1817 accepted as Lampsilis ovata (Say, 1817)
- Species Unio oviformis Conrad, 1834 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio ovoideus (Gozhik, 2002) †
- Species Unio oxyrhynchus E. von Martens, 1861 accepted as Lanceolaria oxyrhyncha (E. von Martens, 1861)
- Species Unio ozarkensis Call, 1887 accepted as Fusconaia ozarkensis (Call, 1887)
- Species Unio pachyodon Ludwig, 1863 † accepted as Pseudunio auricularius (Spengler, 1793)
- Species Unio pachysoma W. H. Benson, 1862 accepted as Indonaia corbis (Hanley, 1856)
- Species Unio padanus Bourguignat, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio pahangensis E. A. Smith, 1899 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio paivaeanus [sic] accepted as Contradens contradens (I. Lea, 1838)
- Species Unio paivanus Morelet, 1865 accepted as Lens contradens (I. Lea, 1838)
- Species Unio pajakomboensis Bullen, 1906 accepted as Lens contradens (I. Lea, 1838)
- Species Unio palembangensis Strubell, 1897 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio paletsensis Yakushina, 1973 †
- Species Unio pallasi E. von Martens, 1874 † accepted as Heterunio pallasi (E. von Martens, 1874) †
- Species Unio pallens Rossmässler, 1842 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio pallescens I. Lea, 1845 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio pallidofulvus I. Lea, 1861 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio paludicolus A. Gould, 1845 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio paludosus Morelet, 1849 accepted as Delphinonaias largillierti (R. A. Philippi, 1847)
- Species Unio palustris Drouët, 1896 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio pamisinus Drouët, 1894 accepted as Potomida acarnanica (Kobelt, 1878)
- Species Unio panacoensis R. A. Philippi, 1843 accepted as Disconaias panacoensis (R. A. Philippi, 1843)
- Species Unio pannonicus Neumayr, 1875 † accepted as Psilunio (Psilunio) pannonicus (Neumayr, 1875) †
- Species Unio pantoensis Neumayr, 1899 accepted as Inversidens pantoensis (Neumayr, 1899)
- Species Unio papiolensis Almera & Bofill y Poch, 1894 †
- Species Unio papyraceus A. Gould, 1845 accepted as Villosa amygdalum (I. Lea, 1843)
- Species Unio paraguayanus E. von Martens, 1895 accepted as Rhipidodonta variabilis (Maton, 1811)
- Species Unio paraguayensis I. Lea, 1866 accepted as Diplodon delodonta (Lamarck, 1819)
- Species Unio paraholmesianus Yen, 1954 † accepted as Nippononaia paraholmesiana (Yen, 1954) †
- Species Unio paralellus (Conrad, 1841) accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio parallelopipedon I. Lea, 1834 accepted as Diplodon parallelopipedon (I. Lea, 1834)
- Species Unio parallelus Conrad, 1841 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio parallelus J. De C. Sowerby, 1840 † accepted as Edmondia accipiens (J. De C. Sowerby, 1840) †
- Species Unio paramattensis I. Lea, 1862 accepted as Hyridella depressa (Lamarck, 1819)
- Species Unio paranensis I. Lea, 1834 accepted as Rhipidodonta paranensis (I. Lea, 1834)
- Species Unio parcus I. Lea, 1866 accepted as Rhipidodonta charruana (A. d'Orbigny, 1835)
- Species Unio parma G. B. Sowerby II, 1868 accepted as Leoparreysia tavoyensis (A. Gould, 1843)
- Species Unio partschi Penecke, 1883 †
- Species Unio parvulus I. Lea, 1860 accepted as Medionidus parvulus (I. Lea, 1860)
- Species Unio parvus Barnes, 1823 accepted as Toxolasma parvum (Barnes, 1823)
- Species Unio paschalis Heude, 1883 accepted as Lamprotula paschalis (Heude, 1883)
- Species Unio pascoei (Prashad, 1928) † accepted as Indonaia pascoei Prashad, 1928 †
- Species Unio patagonica A. d'Orbigny, 1835 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio patapscoensis W. B. Clark, 1911 †
- Species Unio patelloides I. Lea, 1860 accepted as Diplodon rhombeus (Spix, 1827)
- Species Unio patrangensis Morlet, 1904 accepted as Hyriopsis myersiana (I. Lea, 1856)
- Species Unio pattinoides I. Lea, 1871 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio patulus I. Lea, 1829 accepted as Pleurobema clava (Lamarck, 1819)
- Species Unio pauciplicatus I. Lea, 1872 accepted as Amblema plicata (Say, 1817)
- Species Unio pauli Neumayr, 1875 † accepted as Potomida bielzi (Czekelius, 1864) †
- Species Unio paulista Ihering, 1893 accepted as Diplodon paulistus (Ihering, 1893)
- Species Unio paulus I. Lea, 1840 accepted as Toxolasma paulum (I. Lea, 1840)
- Species Unio pauperculus I. Lea, 1861 accepted as Rotundaria asperata (I. Lea, 1861)
- Species Unio paviei Morlet, 1891 accepted as Chamberlainia hainesiana (I. Lea, 1856)
- Species Unio pavlovi G. I. Popov, 1970 †
- Species Unio pavlovici Brusina, 1902 †
- Species Unio pawensis I. Lea, 1868 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio paxi Pavlović, 1931 †
- Species Unio pazii I. Lea, 1862 accepted as Ensidens ingallsianus (I. Lea, 1852)
- Species Unio pealei I. Lea, 1871 accepted as Obovaria olivaria (Rafinesque, 1820)
- Species Unio pearlensis Conrad, 1855 accepted as Amblema plicata (Say, 1817)
- Species Unio pectinatus (Spix, 1827) accepted as Castalia ambigua Lamarck, 1819
- Species Unio pectitus Conrad, 1854 accepted as Epioblasma obliquata (Rafinesque, 1820)
- Species Unio pectorosus Conrad, 1834 accepted as Lampsilis pectorosa (Conrad, 1834)
- Species Unio peculiaris I. Lea, 1866 accepted as Diplodon wymanii (I. Lea, 1860)
- Species Unio peguensis J. G. Anthony, 1865 accepted as Yaukthwa peguensis (J. G. Anthony, 1865)
- Species Unio pellislacerti Morelet, 1865 accepted as Scabies scobinatus (I. Lea, 1856)
- Species Unio pellucidus I. Lea, 1845 accepted as Villosa vibex (Conrad, 1834)
- Species Unio peneckei Brusina, 1902 † accepted as Cuneopsidea oriovacensis (M. Hörnes, 1864) †
- Species Unio penicillatus I. Lea, 1857 accepted as Medionidus penicillatus (I. Lea, 1857)
- Species Unio penitus Conrad, 1834 accepted as Epioblasma penita (Conrad, 1834)
- Species Unio pensitatus P. Fischer & Crosse, 1894 accepted as Ctenodesma borneensis (Issel, 1874)
- Species Unio penultimus Gabb, 1864 †
- Species Unio pequottinus Linsley, 1845
- Species Unio peraeformis I. Lea, 1860 accepted as Rhipidodonta peraeformis (I. Lea, 1860)
- Species Unio perakensis Preston, 1912 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio perakensis de Morgan, 1886 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio percoarctatus I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio percompressus E. von Martens, 1887 accepted as Psoronaias percompressa (E. von Martens, 1887)
- Species Unio percorrugata Whitfield, 1903 † accepted as Proparreysia percorrugata (Whitfield, 1903) †
- Species Unio perdeclivis Lindholm, 1932 † accepted as Betekeia perdeclivis (Lindholm, 1932) †
- Species Unio perdix I. Lea, 1834 accepted as Ortmanniana pectorosa (Conrad, 1834)
- Species Unio perlatus I. Lea, 1863 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio perlucens I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio permiscens I. Lea, 1859 accepted as Potamilus purpuratus (Lamarck, 1819)
- Species Unio permusculosus Meek, 1876 †
- Species Unio pernodosus I. Lea, 1845 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio perovalis Conrad, 1834 accepted as Hamiota perovalis (Conrad, 1834)
- Species Unio perovatus Conrad, 1834 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio perpastus I. Lea, 1861 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio perpictus I. Lea, 1860 accepted as Villosa iris (I. Lea, 1829)
- Species Unio perplexus I. Lea, 1831 accepted as Epioblasma torulosa (Rafinesque, 1820)
- Species Unio perplexus Say, 1829 accepted as Epioblasma obliquata (Rafinesque, 1820)
- Species Unio perplicatus Conrad, 1841 accepted as Amblema plicata (Say, 1817)
- Species Unio perpurpureus I. Lea, 1861 accepted as Villosa perpurpurea (I. Lea, 1861)
- Species Unio perradiatus I. Lea, 1858 accepted as Lampsilis fasciola Rafinesque, 1820
- Species Unio personatus Say, 1829 accepted as Epioblasma personata (Say, 1829)
- Species Unio perstriatus I. Lea, 1852 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio persulcatus I. Lea, 1859 accepted as Nephronaias calamitarum (Morelet, 1849)
- Species Unio pertennis De Gregorio, 1914 accepted as Toxolasma parvum (Barnes, 1823)
- Species Unio pertenuis I. Lea, 1863 accepted as Lasmigona subviridis (Conrad, 1835)
- Species Unio peruciensis Frič, 1869 †
- Species Unio peruviana Lamarck, 1819 accepted as Amblema plicata (Say, 1817)
- Species Unio petersi Penecke, 1883 † accepted as Unio thalassinus Brusina, 1874 †
- Species Unio petkovici Pavlović, 1931 †
- Species Unio petrboki Modell, 1930 †
- Species Unio petrinus A. Gould, 1855 accepted as Rotundaria petrina (A. Gould, 1855)
- Species Unio petrinus C. A. White, 1876 † accepted as Unio couesi C. A. White, 1877 †
- Species Unio petrovichii Küster, 1854 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio petrovski Popova, 1963 † accepted as Nodularia petrovski (Popova, 1963) †
- Species Unio petterianus Küster, 1854 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio pfeifferi Dunker, 1849 accepted as Diplodon multistriatus (I. Lea, 1831)
- Species Unio pfisteri Heude, 1874 accepted as Ptychorhynchus pfisteri (Heude, 1874)
- Species Unio phaselus I. Lea, 1856 accepted as Scabies phaselus (I. Lea, 1856)
- Species Unio phaseolus Hildreth, 1828 accepted as Ptychobranchus fasciolaris (Rafinesque, 1820)
- Species Unio phaseolus Kobelt, 1878 accepted as Unio crassus Philipsson, 1788
- Species Unio phaseolus J. De C. Sowerby, 1840 † accepted as Carbonicola aquilina (J. De C. Sowerby, 1840) †
- Species Unio philippianus Küster, 1861 accepted as Velesunio ambiguus (R. A. Philippi, 1847)
- Species Unio phillipsii Conrad, 1835 accepted as Obliquaria reflexa Rafinesque, 1820
- Species Unio phillipsii W. C. Williamson, 1836 † accepted as Anthraconauta phillipsii (W. C. Williamson, 1836) †
- Species Unio piandanshanensis X.-Z. Liu, 1984 †
- Species Unio pianensis Farines, 1833 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio piccinellii Adami, 1886 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio piceus I. Lea, 1860 accepted as Diplodon piceus (I. Lea, 1860)
- Species Unio picteti Locard, 1893 †
- Species Unio pictoriformis B. I. Chernyshev, 1937 † accepted as Proarcidopsis pictoriformis (B. I. Chernyshev, 1937) †
- Species Unio pictorum (Linnaeus, 1758)
- Species Unio pictus I. Lea, 1834 accepted as Cambarunio taeniatus pictus (I. Lea, 1834)
- Species Unio pietri Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio piger I. Lea, 1860 accepted as Diplodon uruguayensis (I. Lea, 1860)
- Species Unio pigerrimus Crosse & P. Fischer, 1894 accepted as Barynaias pigerrima (Crosse & P. Fischer, 1894)
- Species Unio pilari Brusina, 1874 † accepted as Rugunio pilari (Brusina, 1874) †
- Species Unio pilaris I. Lea, 1840 accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio pilatus I. Lea, 1866 accepted as Radiatula pilata (I. Lea, 1866)
- Species Unio pileus I. Lea, 1831 accepted as Epioblasma personata (Say, 1829)
- Species Unio pilgrimi B. B. Gupta, 1930 †
- Species Unio pillae De Stefani, 1880 †
- Species Unio pillai [sic] † accepted as Unio pillae De Stefani, 1880 †
- Species Unio pilsbryi W. A. Marsh, 1891 accepted as Amblema plicata (Say, 1817)
- Species Unio pinax W. H. Benson, 1862 accepted as Parreysia nagpoorensis (I. Lea, 1860)
- Species Unio pinchonianus Heude, 1883 accepted as Ptychorhynchus murinum (Heude, 1883)
- Species Unio pinei B. H. Wright, 1897 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio pinguis I. Lea, 1857 accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio pinguis F. Sandberger, 1861 † accepted as Potomida littoralis eyerdami Modell, 1950 †
- Species Unio pinkstonii S. H. Wright, 1897 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio pisciculus Heude, 1874 accepted as Tchangsinaia piscicula (Heude, 1874)
- Species Unio placidus Küster, 1862 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio placitus I. Lea, 1852 accepted as Hamiota perovalis (Conrad, 1834)
- Species Unio plagiosoma W. H. Benson, 1862 accepted as Parreysia plagiosoma (W. H. Benson, 1862)
- Species Unio plancus I. Lea, 1860 accepted as Villosa nebulosa (Conrad, 1834)
- Species Unio planiapicus X.-Z. Liu, 1984 †
- Species Unio planicostatus I. Lea, 1860 accepted as Cambarunio nebulosus (Conrad, 1834)
- Species Unio planilateris Conrad, 1838 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio planior I. Lea, 1868 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio planivalis Morelet, 1851
- Species Unio plantii I. Lea, 1857 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio planulatus I. Lea, 1829 accepted as Ptychobranchus fasciolaris (Rafinesque, 1820)
- Species Unio planus Barnes, 1823 accepted as Leptodea fragilis (Rafinesque, 1820)
- Species Unio planus Studer, 1820 accepted as Unio crassus Philipsson, 1788
- Species Unio planus F. A. Roemer, 1836 †
- Species Unio platyrhynchus Rossmässler, 1835 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio pleasii W. A. Marsh, 1891 accepted as Venustaconcha pleasii (W. A. Marsh, 1891)
- Species Unio plebeius Drouët, 1888 accepted as Unio mancus Lamarck, 1819
- Species Unio plectophorus Conrad, 1849 accepted as Elliptoideus sloatianus (I. Lea, 1840)
- Species Unio plectrophorus Conrad, 1849 accepted as Elliptoideus sloatianus (I. Lea, 1840)
- Species Unio plenus I. Lea, 1840 accepted as Pleurobema plenum (I. Lea, 1840)
- Species Unio plexus Conrad, 1838 accepted as Barynaias plexus (Conrad, 1838)
- Species Unio plicata Say, 1817 accepted as Amblema plicata (Say, 1817)
- Species Unio plicatulus I. Lea, 1859 accepted as Ctenodesma borneensis (Issel, 1874)
- Species Unio plicatulus Küster, 1856 accepted as Nephronaias plicatula (Küster, 1856)
- Species Unio pliciferus I. Lea, 1838 accepted as Barynaias plexus (Conrad, 1838)
- Species Unio pliculosus E. von Martens, 1894 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio plostinae Teisseyre, 1911 † accepted as Psilunio (Psilunio) plostinae (Teisseyre, 1911) †
- Species Unio poeyanus I. Lea, 1857 accepted as Nephritica poeyana (I. Lea, 1857)
- Species Unio polejaievi Bogachev, 1908 †
- Species Unio politus Conrad, 1837 accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio pollonerae Sacco, 1889 †
- Species Unio polmontensis T. Brown, 1849 † accepted as Carbonicola polmontensis (T. Brown, 1849) †
- Species Unio polymorphus B. H. Wright, 1899 accepted as Elliptio monroensis (I. Lea, 1843)
- Species Unio polystictus Heude, 1877 accepted as Gibbosula polysticta (Heude, 1877)
- Species Unio ponderosus Rossmässler, 1842 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio ponticus Jatsko, 1954 † accepted as Betekeia pontica (Jatsko, 1954) †
- Species Unio popeii I. Lea, 1857 accepted as Popenaias popeii (I. Lea, 1857)
- Species Unio popenoi Call, 1885 accepted as Cyprogenia aberti (Conrad, 1850)
- Species Unio porphyreus I. Lea, 1861 accepted as Villosa umbrans (I. Lea, 1857)
- Species Unio porrectus Conrad, 1854 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio porrectus J. De C. Sowerby, 1828 †
- Species Unio portisii Pollonera, 1888 †
- Species Unio porumbari Tournouër, 1880 † accepted as Sulcopotomida porumbarui (Tournouër, 1880) †
- Species Unio porumbarui Penecke, 1883 † accepted as Cuneopsidea oriovacensis (M. Hörnes, 1864) †
- Species Unio postbiplicata Whitfield, 1903 † accepted as Plesielliptio postbiplicatus (Whitfield, 1903) †
- Species Unio postbiplicatus Whitfield, 1903 † accepted as Plesielliptio postbiplicatus (Whitfield, 1903) †
- Species Unio postellii I. Lea, 1858 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio postumus Rochebrune, 1904 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio postumus Bogachev, 1961 † accepted as Bogatschevia postumus (Bogachev, 1961) †
- Species Unio poulsoni Conrad, 1834 accepted as Potamilus purpuratus (Lamarck, 1819)
- Species Unio powellii I. Lea, 1852 accepted as Lampsilis powellii (I. Lea, 1852)
- Species Unio praeanodontoides Whitfield, 1885 † accepted as Sagittunio nasutus (Say, 1817)
- Species Unio praecrassoides (Sidnev, 1976) †
- Species Unio praedemissus (Ludwig, 1865) †
- Species Unio praelevantinus Bogachev, 1961 †
- Species Unio praelongus Barnes, 1823 accepted as Ligumia recta (Lamarck, 1819)
- Species Unio praenovorossicus Andrusov, 1917 †
- Species Unio praeposterus Küster, 1853 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio praequadratus B.-L. Ding & J.-H. Li, 1982 †
- Species Unio praerobustus (Gozhik, 2006) †
- Species Unio prahovensis Botez, 1914 †
- Species Unio prashadi Chepalyga, 1967 †
- Species Unio prasinatus Conrad, 1866 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio prasinus Conrad, 1834 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio prattii I. Lea, 1858 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio premorsus Rafinesque, 1831 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio preobrazhenskii Lindholm, 1932 † accepted as Heterunio preobrazhenskii (Lindholm, 1932) †
- Species Unio pressirostris E. von Martens, 1900 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio pressus I. Lea, 1843 accepted as Lasmigona compressa (I. Lea, 1829)
- Species Unio prestwichi Kennard & B. B. Woodward, 1924 †
- Species Unio prevostianus I. Lea, 1852 accepted as Villosa vibex (Conrad, 1834)
- Species Unio prigorovskii Bogachev, 1961 † accepted as Nodularia prigorovskii (Bogachev, 1961) †
- Species Unio primaevus C. A. White, 1877 † accepted as Quadrula primaevus (C. A. White, 1877) †
- Species Unio priscus Meek & Hayden, 1856 † accepted as Plesielliptio priscus (Meek & Hayden, 1856) †
- Species Unio pristinus Bielz, 1864 † accepted as Pristinunio pristinus (Bielz, 1864) †
- Species Unio proavitus C. A. White, 1877 † accepted as Pleurobema proavitum (C. A. White, 1877) †
- Species Unio problematicus Klipstein, 1843 †
- Species Unio procumbens T. Fuchs, 1870 † accepted as Pristinunio pristinus (Bielz, 1864) †
- Species Unio productior I. Lea, 1852 accepted as Elongaria orientalis (I. Lea, 1840)
- Species Unio productus Conrad, 1836 accepted as Elliptio producta (Conrad, 1836)
- Species Unio productus Mousson, 1849 accepted as Elongaria orientalis (I. Lea, 1840)
- Species Unio profugus A. Gould, 1850 accepted as Alathyria profuga (A. Gould, 1850)
- Species Unio proindifferens Jatsko, 1972 †
- Species Unio prolongatus Drouët, 1894 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio prominulus Stefanescu, 1889 † accepted as Potomida prominula (Stefanescu, 1889) †
- Species Unio pronus E. von Martens, 1874 † accepted as Rhombuniopsis (Bogatschevinaia) prona (E. von Martens, 1874) †
- Species Unio propecoelatus De Gregorio, 1914 accepted as Pegias fabula (I. Lea, 1838)
- Species Unio propesulcatus De Gregorio, 1914 accepted as Epioblasma obliquata (Rafinesque, 1820)
- Species Unio propeverutus De Gregorio, 1914 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio propheticus C. A. White, 1876 † accepted as Epioblasma prophetica (C. A. White, 1876) †
- Species Unio propinquus I. Lea, 1857 accepted as Epioblasma propinqua (I. Lea, 1857)
- Species Unio proprius I. Lea, 1865 accepted as Villosa umbrans (I. Lea, 1857)
- Species Unio prosacrus Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio protensus I. Lea, 1865 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio protensus Tapparone Canefri, 1889 accepted as Trapezidens dolichorhynchus (Tapparone Canefri, 1889)
- Species Unio protovittatus Hale & Tindale, 1930 accepted as Velesunio ambiguus (R. A. Philippi, 1847)
- Species Unio protractus Lindholm, 1932 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio proximus I. Lea, 1852 accepted as Villosa delumbis (Conrad, 1834)
- Species Unio prunoides I. Lea, 1868 accepted as Anodontites cylindracea (I. Lea, 1838)
- Species Unio prusii Bourguignat, 1856 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio psammactinus R. A. Philippi, 1849 accepted as Diplodon multistriatus (I. Lea, 1831)
- Species Unio psammoica A. d'Orbigny, 1835 accepted as Castalia psammoica (A. d'Orbigny, 1835)
- Species Unio pseudatavus Bukowski, 1896 †
- Species Unio pseudendlichi Yen, 1954 †
- Species Unio pseudochasaricus Chepalyga, 1967 †
- Species Unio pseudodistortus Martinson, 1951 † accepted as Nodularia pseudodistorta (Martinson, 1951) †
- Species Unio pseudolitoralis Clessin, 1877 accepted as Unio crassus Philipsson, 1788
- Species Unio pseudolittoralis [sic] accepted as Unio pseudolitoralis Clessin, 1877
- Species Unio pseudomargaritana Martinson, 1957 † accepted as Unio pseudomargaritanus Martinson, 1957 †
- Species Unio pseudomargaritanus Martinson, 1957 †
- Species Unio pseudomoldavicus Bogachev, 1924 †
- Species Unio pseudonovorossicus Jatsko, 1954 † accepted as Betekeia pseudonovorossica (Jatsko, 1954) †
- Species Unio pseudonymus C. T. Simpson, 1900 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio pseudoptychodes Teisseyre, 1911 †
- Species Unio pseudosturi Halaváts, 1888 † accepted as Potomida wilhelmi (Penecke, 1883) †
- Species Unio psilodontum Teisseyre, 1907 † accepted as Psilunio psilodontum (Teisseyre, 1907) †
- Species Unio psoricus Morelet, 1851 accepted as Psoronaias semigranosa (R. A. Philippi, 1843)
- Species Unio pterophorus Brusina, 1878 † accepted as Hyriopsis pterophora (Brusina, 1878) †
- Species Unio ptychodes Brusina, 1874 † accepted as Psilunio (Psilunio) bielzi (Czekelius, 1864) †
- Species Unio pucici Brusina, 1902 † accepted as Margaritifera pucici (Brusina, 1902) †
- Species Unio pudicus I. Lea, 1860 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio pugio W. H. Benson, 1862 accepted as Indochinella pugio (W. H. Benson, 1862)
- Species Unio pugiunculus Blanford, 1883 † accepted as Nodularia pugiuncula (Blanford, 1883) †
- Species Unio pulcher I. Lea, 1838 accepted as Cambarunio taeniatus pictus (I. Lea, 1834)
- Species Unio pulcher Tapparone Canefri, 1889 accepted as Lamellidens generosus (A. Gould, 1847)
- Species Unio pullatis I. Lea, 1857 accepted as Unio pullatus I. Lea, 1857
- Species Unio pullatus I. Lea, 1857 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio pullescens I. Lea, 1845 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio pullus Conrad, 1838 accepted as Toxolasma pullum (Conrad, 1838)
- Species Unio pulvinulus I. Lea, 1845 accepted as Pleurobema rubellum (Conrad, 1834)
- Species Unio pumilus I. Lea, 1838 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio punctatus I. Lea, 1865 accepted as Cambarunio taeniatus punctatus (I. Lea, 1865)
- Species Unio puniceus Haldeman, 1842 accepted as Villosa iris (I. Lea, 1829)
- Species Unio purpurascens Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio purpurata Lamarck, 1819 accepted as Potamilus purpuratus (Lamarck, 1819)
- Species Unio purpurellus I. Lea, 1857 accepted as Elliptio purpurella (I. Lea, 1857)
- Species Unio purpureus Say, 1817 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio purpuriatus Say, 1831 accepted as Disconaias purpuriata (Say, 1831)
- Species Unio purus I. Lea, 1858 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio pusillus I. Lea, 1840 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio pustulata Swainson, 1840 accepted as Tritogonia verrucosa (Rafinesque, 1820)
- Species Unio pustulatus I. Lea, 1831 accepted as Rotundaria nodulata (Rafinesque, 1820)
- Species Unio pustulosus I. Lea, 1831 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio pybasii I. Lea, 1858 accepted as Villosa vanuxemensis (I. Lea, 1838)
- Species Unio pygmaeiformis Martinson, 1957 †
- Species Unio pygmaeus I. Lea, 1852 accepted as Lasmigona subviridis (Conrad, 1835)
- Species Unio pyramidalus [sic] † accepted as Carbonicola pyramidata (T. Brown, 1843) †
- Species Unio pyramidatoides Whitfield, 1907 † accepted as Proparreysia pyramidatoides (Whitfield, 1907) †
- Species Unio pyramidatus I. Lea, 1831 accepted as Pleurobema rubrum (Rafinesque, 1820)
- Species Unio pyramidellus Whitfield, 1907 † accepted as Proparreysia pyramidella (Whitfield, 1907) †
- Species Unio pyriformis I. Lea, 1857 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio qianweiensis X.-Z. Liu & Luo, 1978 †
- Species Unio qingshuiheensis B.-Y. Huang & J.-M. Wei, 1976 †
- Species Unio quadrangulosus Heude, 1881 accepted as Lamprotula quadrangulosa (Heude, 1881)
- Species Unio quadrans I. Lea, 1860 accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio quadratus I. Lea, 1859 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio quadrilaterus I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio quadrulus (Rafinesque, 1820) accepted as Quadrula quadrula (Rafinesque, 1820)
- Species Unio quadruus Soós, 1956 †
- Species Unio quaternellus Mabille, 1889
- Species Unio quinqueannulatus Küster, 1854 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio quintardii Cragin, 1887 accepted as Amblema plicata (Say, 1817)
- Species Unio rackianus Brusina, 1874 †
- Species Unio raddei Drouët, 1881 accepted as Unio crassus Philipsson, 1788
- Species Unio raddei Brusina, 1902 † accepted as Unio haeckeli Penecke, 1883 †
- Species Unio radians I. Lea, 1857 accepted as Villosa nebulosa (Conrad, 1834)
- Species Unio radiatodentatus Sinzov, 1897 † accepted as Psilunio radiatodentatus (Sinzov, 1897) †
- Species Unio radiatoides I. Lea, 1868 † accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio radiatus (Gmelin, 1791) accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio radiolus I. Lea, 1871 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio radiosus I. Lea, 1871 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio radovanovici Pavlović, 1931 †
- Species Unio radula Say, 1829
- Species Unio radula Hanley, 1856 accepted as Pseudoscabies scobina (Hanley, 1856)
- Species Unio radulosus Drouët & Chaper, 1892 accepted as Discomya radulosa (Drouët & Chaper, 1892)
- Species Unio raeensis I. Lea, 1859 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio rafinesquei Vanatta, 1915 accepted as Elliptio occulta (I. Lea, 1843)
- Species Unio ragosini [sic] † accepted as Unio ragozinii Lebedev, 1958 †
- Species Unio ragozinii Lebedev, 1958 †
- Species Unio rajahensis I. Lea, 1841 accepted as Parreysia rajahensis (I. Lea, 1841)
- Species Unio rakovacianus [sic] † accepted as Unio rakovecianus Brusina, 1874 †
- Species Unio rakovecianus Brusina, 1874 †
- Species Unio raleighensis I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio randabeli Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio rangianus I. Lea, 1838 accepted as Epioblasma rangiana (I. Lea, 1838)
- Species Unio rariplicata Lamarck, 1819 accepted as Amblema plicata (Say, 1817)
- Species Unio rarisulcata Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio rasus I. Lea, 1863 accepted as Unio tigridis Bourguignat, 1852
- Species Unio ratidotus Charmes, 1885 accepted as Coelatura ratidota (Charmes, 1885)
- Species Unio ratus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio raveneli Conrad, 1834 accepted as Elliptio raveneli (Conrad, 1834)
- Species Unio ravenelianus I. Lea, 1834 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio ravistellus Morelet, 1849 accepted as Nephronaias ravistella (Morelet, 1849)
- Species Unio ravoisieri Deshayes, 1848
- Species Unio raymondi Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio raymondopsis Kobelt, 1913 accepted as Unio terminalis Bourguignat, 1852
- Species Unio raymondopsis Kobelt, 1912 accepted as Unio terminalis Bourguignat, 1852
- Species Unio reclusus B. H. Wright, 1898 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio recta Lamarck, 1819 accepted as Ligumia recta (Lamarck, 1819)
- Species Unio rectangularis Tapparone Canefri, 1889 accepted as Yaukthwa rectangularis (Tapparone Canefri, 1889)
- Species Unio rectilinearis G. B. Sowerby II, 1868
- Species Unio rectoides C. A. White, 1886 † accepted as Ligumia whitei (J. Henderson, 1918) †
- Species Unio rectoides Whitfield, 1885 † accepted as Ligumia recta (Lamarck, 1819)
- Species Unio rectus (Lamarck, 1819) accepted as Ligumia recta (Lamarck, 1819)
- Species Unio recurrens Penecke, 1883 †
- Species Unio recurvatus I. Lea, 1871 accepted as Pleuronaia dolabelloides (I. Lea, 1840)
- Species Unio reesideanus Yen, 1951 †
- Species Unio reesidei Stanton, 1916 † accepted as Amblema reesidei (Stanton, 1916) †
- Species Unio reesidei Yen, 1951 † accepted as Unio reesideanus Yen, 1951 †
- Species Unio reeveianus I. Lea, 1852 accepted as Lampsilis reeveiana (I. Lea, 1852)
- Species Unio refulgens I. Lea, 1868 accepted as Cyclonaias refulgens (I. Lea, 1868)
- Species Unio regularis I. Lea, 1841 accepted as Villosa iris (I. Lea, 1829)
- Species Unio regularis Frič, 1869 †
- Species Unio reinianus Kobelt, 1879 accepted as Inversiunio reinianus (Kobelt, 1879)
- Species Unio requienii Michaud, 1831 accepted as Unio mancus requienii Michaud, 1831
- Species Unio retiarius Heude, 1883 accepted as Acuticosta retiaria (Heude, 1883)
- Species Unio retrolatus X.-Z. Liu, 1988 †
- Species Unio retusa Lamarck, 1819 accepted as Obovaria retusa (Lamarck, 1819)
- Species Unio retusoides Whitfield, 1903 † accepted as Proparreysia retusoides (Whitfield, 1903) †
- Species Unio rhenanus Kobelt, 1886 accepted as Unio tumidus Philipsson, 1788
- Species Unio rhindii (T. Brown, 1843) † accepted as Carbonicola rhindii (T. Brown, 1843) †
- Species Unio rhombeus Spix, 1827 accepted as Diplodon rhombeus (Spix, 1827)
- Species Unio rhomboideus Moquin-Tandon, 1855 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio rhomboidopsis Locard, 1883 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio rhombula Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio rhuacoica A. d'Orbigny, 1835 accepted as Diplodon rhuacoicus (A. d'Orbigny, 1835)
- Species Unio rhuaconicus Küster, 1856 accepted as Diplodon ellipticus Spix, 1827
- Species Unio ribeiroi Fontannes, 1883 † accepted as Margaritifera (Pseudunio) flabellata (Goldfuss, 1837) †
- Species Unio riddellii I. Lea, 1862 accepted as Pleurobema riddellii (I. Lea, 1862)
- Species Unio ridibundus Say, 1829 accepted as Epioblasma obliquata (Rafinesque, 1820)
- Species Unio riphaei G. I. Popov, 1965 † accepted as Bogatschevia tamanensis riphaei (G. I. Popov, 1965) †
- Species Unio riphaeicus B. I. Chernyshev, 1956 † accepted as Unio korkinensis B. I. Chernyshev, 1937 †
- Species Unio rivicolus Conrad, 1868 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio rivularis Conrad, 1853 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio rivularis Moquin-Tandon, 1856 accepted as Unio crassus Philipsson, 1788
- Species Unio roanokensis I. Lea, 1838 accepted as Elliptio roanokensis (I. Lea, 1838)
- Species Unio roanokoides I. Lea, 1868 † accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio robustus Lindholm, 1932 † accepted as Betekeia athleta (Lindholm, 1932) †
- Species Unio robustus Drouët, 1879 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio robustus J. De C. Sowerby, 1840 † accepted as Carbonicola robusta (J. De C. Sowerby, 1823) †
- Species Unio rochechouartii Heude, 1875 accepted as Gibbosula rochechouartii (Heude, 1875)
- Species Unio roemeri Dunker, 1843 †
- Species Unio roeperti H. A. C. Berger, 1854 †
- Species Unio roici Brusina, 1902 †
- Species Unio roissyi Michaud, 1831 accepted as Margaritifera margaritifera (Linnaeus, 1758)
- Species Unio rollei Kobelt & Rolle, 1895 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio rongxianensis X.-Z. Liu, 1984 †
- Species Unio rosaceus DeKay, 1843 accepted as Lampsilis siliquoidea (Barnes, 1823)
- Species Unio rosaceus Conrad, 1849 accepted as Leptodea ochracea (Say, 1817)
- Species Unio rosseti Cobălcescu, 1883 † accepted as Psilunio craiovensis (Tournouër, 1880) †
- Species Unio rostellum I. Lea, 1872 accepted as Elliptio folliculata (I. Lea, 1838)
- Species Unio rostraeformis I. Lea, 1857 accepted as Elliptio producta (Conrad, 1836)
- Species Unio rostralis E. von Martens, 1897 accepted as Grandidieria burtoni (S. P. Woodward, 1859)
- Species Unio rostrata Lamarck, 1819 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio rostratus Lamarck, 1819 accepted as Unio rostrata Lamarck, 1819
- Species Unio rostriformis "I. Lea, 1858" accepted as Unio rostraeformis I. Lea, 1857
- Species Unio rostrum I. Lea, 1862 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio roswellensis I. Lea, 1858 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio rothi Bourguignat, 1865 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio rotulatus B. H. Wright, 1899 accepted as Reginaia rotulata (B. H. Wright, 1899)
- Species Unio rotundata Lamarck, 1819 accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio rotundatus (Lamarck, 1819) accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio rotundus Spix, 1827 accepted as Diplodon rotundus (Spix, 1827)
- Species Unio rouxii Noulet, 1855 † accepted as Palindonaia solandri (J. De C. Sowerby, 1826) †
- Species Unio rowellii I. Lea, 1859 accepted as Nephronaias rowellii (I. Lea, 1859)
- Species Unio rubellinus I. Lea, 1857 accepted as Medionidus acutissimus (I. Lea, 1831)
- Species Unio rubellus Conrad, 1834 accepted as Pleurobema rubellum (Conrad, 1834)
- Species Unio rubens Menke, 1828 accepted as Unio crassus Philipsson, 1788
- Species Unio rubicundus E. von Martens, 1900 accepted as Martensnaias rubicunda (E. von Martens, 1900)
- Species Unio rubidus I. Lea, 1861 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio rubiginosus I. Lea, 1829 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio rudis Conrad, 1837 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio rudus I. Lea, 1859 accepted as Diplodon delodonta (Lamarck, 1819)
- Species Unio ruellani Bourguignat, 1883 accepted as Coelatura hauttecoeuri (Bourguignat, 1883)
- Species Unio rufescens Heude, 1874 accepted as Cuneopsis rufescens (Heude, 1874)
- Species Unio ruffonii Adami, 1886 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio rufofuscus I. Lea, 1865 accepted as Diplodon gratus (I. Lea, 1860)
- Species Unio rufus I. Lea, 1857 accepted as Elliptio arca (Conrad, 1834)
- Species Unio rufusculus I. Lea, 1852 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio rugatus F. W. Hutton, 1883 accepted as Echyridella menziesii (J. E. Gray, 1843)
- Species Unio rugifer Küster, 1856 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio rugososulcatus I. Lea, 1866 accepted as Pachynaias rugososulcata (I. Lea, 1866)
- Species Unio rugosus Barnes, 1823 accepted as Quadrula quadrula (Rafinesque, 1820)
- Species Unio rugosus Anton, 1838
- Species Unio rugosus (T. Brown, 1843) † accepted as Carbonicola rugosa (T. Brown, 1843) †
- Species Unio rugulosus Küster, 1856 accepted as Nephronaias rugulosa (Küster, 1856)
- Species Unio rugulosus J. Phillips, 1839 † accepted as Curvirimula scotica (Etheridge, 1877) †
- Species Unio rumanus Tournouër, 1879 † accepted as Rumanunio rumanus (Tournouër, 1879) †
- Species Unio rumphianus I. Lea, 1852 accepted as Quadrula rumphiana (I. Lea, 1852)
- Species Unio rusani Brusina, 1902 † accepted as Unio pavlovici rusani Brusina, 1902 †
- Species Unio rusticus I. Lea, 1856 accepted as Lens contradens (I. Lea, 1838)
- Species Unio rusticus Pini, 1884 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio rutersvillensis I. Lea, 1859 accepted as Ligumia subrostrata (Say, 1831)
- Species Unio rutilans I. Lea, 1857 accepted as Villosa vibex (Conrad, 1834)
- Species Unio sabbae Ionescu-Argetoaia, 1918 † accepted as Unio prominulus Stefanescu, 1889 †
- Species Unio sabljari Brusina, 1902 † accepted as Cuneopsidea oriovacensis (M. Hörnes, 1864) †
- Species Unio saccatus Küster, 1862 accepted as Epioblasma florentina (I. Lea, 1857)
- Species Unio saccellus Drouët & Chaper, 1892 accepted as Lens lugens (Drouët & Chaper, 1892)
- Species Unio sacculus Reeve, 1864 accepted as Epioblasma florentina (I. Lea, 1857)
- Species Unio sacellus [sic] accepted as Contradens contradens (I. Lea, 1838)
- Species Unio sacsaganis (Jatsko, 1955) †
- Species Unio sageri Conrad, 1836 accepted as Ligumia recta (Lamarck, 1819)
- Species Unio sagittarius I. Lea, 1856 accepted as Ensidens sagittarius (I. Lea, 1856)
- Species Unio sagittiformis I. Lea, 1852 accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio sagorianus Bittner, 1884 †
- Species Unio sagrinatus G. B. Sowerby II, 1868 accepted as Arotonaias cyrenoides (R. A. Philippi, 1847)
- Species Unio saladoensis I. Lea, 1860 accepted as Cyrtonaias saladoensis (I. Lea, 1860)
- Species Unio salamboana Pallary, 1929 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio salebrosus I. Lea, 1859 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio sallei Crosse & P. Fischer, 1893 accepted as Barynaias sallei (Crosse & P. Fischer, 1893)
- Species Unio sampanoides T. Kobayashi, 1968 † accepted as Nakamuranaia (Yunnanoconcha) sampanoides (T. Kobayashi, 1968) †
- Species Unio sampsonii I. Lea, 1862 accepted as Epioblasma sampsonii (I. Lea, 1862)
- Species Unio samuchicus K. A. Ali-Zade, 1939 †
- Species Unio sandbergeri Neumayr, 1875 † accepted as Psilunio sandbergeri (Neumayr, 1875) †
- Species Unio sandersoni P. S. Warren, 1926 † accepted as Lampsilis sandersoni (P. S. Warren, 1926) †
- Species Unio sandrii Rossmässler, 1844 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio sandriopsis Servain, 1886 accepted as Unio crassus Philipsson, 1788
- Species Unio sandrius Dall, 1913 † accepted as Lampsilis sandrius (Dall, 1913) †
- Species Unio santeensis I. Lea, 1871 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio saportae "Matheron" †
- Species Unio sapotalensis I. Lea, 1841 accepted as Actinonaias sapotalensis (I. Lea, 1841)
- Species Unio sapperi Ihering, 1901 accepted as Cyrtonaias sapperi (Ihering, 1901)
- Species Unio saratae Teisseyre, 1907 † accepted as Psilunio saratae (Teisseyre, 1907) †
- Species Unio sartakoviensis Lebedev, 1959 †
- Species Unio satillaensis I. Lea, 1858 accepted as Elliptio downiei (I. Lea, 1858)
- Species Unio satur I. Lea, 1852 accepted as Lampsilis satura (I. Lea, 1852)
- Species Unio saulcyi Bourguignat, 1852 accepted as Leguminaia saulcyi (Bourguignat, 1852)
- Species Unio savannahensis I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio savroni Gozhik, 2006 †
- Species Unio saxeus Conrad, 1838 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio sayanus Conrad, 1838 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio sayii Ward, 1839 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio sayni Fontannes, 1880 †
- Species Unio scalenius (Rafinesque, 1820) accepted as Pleurobema clava (Lamarck, 1819)
- Species Unio scamnatus Morelet, 1849 accepted as Nephronaias scamnata (Morelet, 1849)
- Species Unio schabarowi B. I. Chernyshev, 1937 †
- Species Unio schiracicus Bogachev, 1936 †
- Species Unio schirvanicus Bogachev, 1932 †
- Species Unio schlagintweitianus Modell, 1969 †
- Species Unio schlegelii E. von Martens, 1861 accepted as Sinohyriopsis schlegelii (E. von Martens, 1861)
- Species Unio schleschi Modell, 1935 †
- Species Unio schoedei F. Haas, 1930 accepted as Ptychorhynchus schoedei (F. Haas, 1930)
- Species Unio schomburgianus Heude, 1885 accepted as Ptychorhynchus schomburgianum (Heude, 1885)
- Species Unio schoolcraftensis I. Lea, 1834 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio schrencki Westerlund, 1897 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio schrenkianus Clessin, 1880 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio schuetzenbergeri Porumbaru, 1881 † accepted as Cuneopsidea sculpta (Brusina, 1874) †
- Species Unio schurabensis B. I. Chernyshev, 1937 †
- Species Unio schwarzii Kobelt, 1915 accepted as Unio delicatus I. Lea, 1863
- Species Unio schweinfurthi E. von Martens, 1886 † accepted as Unio abyssinicus E. von Martens, 1866
- Species Unio schwerzenbachi Bourguignat, 1856 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio sciphicus Gozhik, 1978 †
- Species Unio scitulus I. Lea, 1860 accepted as Villosa iris (I. Lea, 1829)
- Species Unio scobina Hanley, 1856 accepted as Pseudoscabies scobina (Hanley, 1856)
- Species Unio scobinatus I. Lea, 1856 accepted as Scabies scobinatus (I. Lea, 1856)
- Species Unio scriptus Heude, 1875 accepted as Aculamprotula scripta (Heude, 1875)
- Species Unio scrobicularioides Frič, 1869 †
- Species Unio sculptus Deshayes, 1874 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio sculptus Brusina, 1874 † accepted as Cuneopsidea sculpta (Brusina, 1874) †
- Species Unio scupiensis Pavlović, 1931 †
- Species Unio scutella Cornuel, 1874 † accepted as Unio scutellus Cornuel, 1874 †
- Species Unio scutellus Cornuel, 1874 †
- Species Unio scutulatus Morelet, 1849 accepted as Delphinonaias scutulata (Morelet, 1849)
- Species Unio scutum G. B. Sowerby II, 1868 accepted as Trapezidens scutum (G. B. Sowerby II, 1868)
- Species Unio securiformis Conrad, 1849 accepted as Pustulosa infucata (Conrad, 1834)
- Species Unio securiformis Ludwig, 1860 † accepted as Carbonicola aquilina (J. De C. Sowerby, 1840) †
- Species Unio securis I. Lea, 1829 accepted as Ellipsaria lineolata (Rafinesque, 1820)
- Species Unio segregatus Drouët, 1896 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio seljani Brusina, 1902 † accepted as Potomida seljani (Brusina, 1902) †
- Species Unio semialatus Deshayes, 1876 accepted as Lens micropterus (Morelet, 1866)
- Species Unio semidecoratus Morlet, 1889 accepted as Lens contradens (I. Lea, 1838)
- Species Unio semigranosus von dem Busch, 1842 accepted as Psoronaias semigranosa (R. A. Philippi, 1843)
- Species Unio semiplicatus Küster, 1862 accepted as Medionidus acutissimus (I. Lea, 1831)
- Species Unio semiplicatus Troschel, 1837
- Species Unio semiquadrata G. B. Sowerby II, 1866 accepted as Lens eximius (I. Lea, 1856)
- Species Unio semirecta Cornuel, 1874 † accepted as Unio semirectus Cornuel, 1874 †
- Species Unio semirectus Cornuel, 1874 †
- Species Unio semirugata Lamarck, 1819 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio semisinensis Martinson, 1951 † accepted as Acuticosta semisinensis (Martinson, 1951) †
- Species Unio semmelinki E. von Martens, 1891 accepted as Lens semmelinki (E. von Martens, 1891)
- Species Unio semseyi Halaváts, 1888 † accepted as Potomida wilhelmi (Penecke, 1883) †
- Species Unio senectus C. A. White, 1877 † accepted as Rhabdotophorus senectus (C. A. White, 1877) †
- Species Unio senex T. Brown, 1849 † accepted as Carbonicola senex (T. Brown, 1849) †
- Species Unio sennaariensis Kuster, 1862 accepted as Coelatura aegyptiaca (Cailliaud, 1823)
- Species Unio sennariensis [sic] accepted as Unio sennaariensis Kuster, 1862
- Species Unio senoai Brusina, 1902 † accepted as Psilunio (Psilunio) senoai (Brusina, 1902) †
- Species Unio serratoradiatus Bogachev, 1961 †
- Species Unio sesirmensis Kobelt, 1913
- Species Unio setubalensis Choffat, 1885 †
- Species Unio sewardi F. R. Woodward, 1971 †
- Species Unio shadini Martinson, 1951 † accepted as Acuticosta shadini (Martinson, 1951) †
- Species Unio shanghaiensis I. Lea, 1859 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio shensiensis M.-C. Chow, 1953 † accepted as Sibireconcha shensiensis (M.-C. Chow, 1953) †
- Species Unio shepardianus I. Lea, 1834 accepted as Elliptio shepardiana (I. Lea, 1834)
- Species Unio shireensis Preston, 1910 accepted as Coelatura mossambicensis (E. von Martens, 1860)
- Species Unio shiziwanensis S.-Y. Cai, 1986 †
- Species Unio shoshonensis C. A. White, 1876 † accepted as Actinonaias shoshonensis (C. A. White, 1876) †
- Species Unio showalterii I. Lea, 1860 accepted as Pleurobema hartmanianum (I. Lea, 1860)
- Species Unio shuangmiaoensis J.-S. Yu, G.-Y. Dong & P.-Y. Yao, 1989 †
- Species Unio shueixigouensis J.-M. Wei, 1984 †
- Species Unio shurtleffianus I. Lea, 1856 accepted as Indonaia shurtleffiana (I. Lea, 1856)
- Species Unio shuttleworthi Küster, 1856
- Species Unio shuttleworthii I. Lea, 1856 accepted as Alathyria pertexta Iredale, 1934
- Species Unio siamensis Morlet, 1889 accepted as Lens micropterus (Morelet, 1866)
- Species Unio siamensis I. Lea, 1866 accepted as Lens misellus (Morelet, 1865)
- Species Unio sibinensis Penecke, 1883 † accepted as Psilunio sibinensis (Penecke, 1883) †
- Species Unio sibiricus Lindholm, 1932 † accepted as Cuneopsis sibirica (Lindholm, 1932) †
- Species Unio sieversi Drouët, 1881 accepted as Unio crassus Philipsson, 1788
- Species Unio sikkimensis I. Lea, 1859 accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio siliguriensis Preston, 1908 accepted as Indonaia gratiosa (R. A. Philippi, 1843)
- Species Unio siliquatus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio siliquoideus Barnes, 1823 accepted as Lampsilis siliquoidea (Barnes, 1823)
- Species Unio silongweensis Preston, 1912 accepted as Unio caffer Krauss, 1848
- Species Unio similis I. Lea, 1857 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio similis (T. Brown, 1843) † accepted as Carbonicola similis (T. Brown, 1843) †
- Species Unio simonis Tristram, 1865 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio simplex I. Lea, 1845 accepted as Ptychobranchus greenii (Conrad, 1834)
- Species Unio simpsoni B. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio simulans I. Lea, 1871 accepted as Pleurobema perovatum (Conrad, 1834)
- Species Unio simus I. Lea, 1838 accepted as Cambarunio simus (I. Lea, 1838)
- Species Unio singleyanus Marsh, 1891 accepted as Villosa amygdalum (I. Lea, 1843)
- Species Unio singularis B. H. Wright, 1899 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio sinopae T. D. A. Cockerell, 1915 † accepted as Margaritifera sinopae (T. D. A. Cockerell, 1915) †
- Species Unio sinuatus Lamarck, 1819 accepted as Pseudunio auricularius (Spengler, 1793)
- Species Unio sinuolata Küster, 1833 accepted as Unio crassus Philipsson, 1788
- Species Unio sinzovi Bogachev, 1924 † accepted as Pleurobema sinzovi (Bogachev, 1924) †
- Species Unio sinzovi Bogachev, 1961 †
- Species Unio siouffi Kobelt, 1912 accepted as Unio tigridis Bourguignat, 1852
- Species Unio sitifensis Morelet, 1851 accepted as Unio durieui Deshayes, 1847
- Species Unio sitsaensis Yakushina, 1964 †
- Species Unio slanicensis Teisseyre, 1907 † accepted as Potomida slanicensis (Teisseyre, 1907) †
- Species Unio slavonicus M. Hörnes, 1864 † accepted as Potomida slavonica (M. Hörnes, 1864) †
- Species Unio sloatianus I. Lea, 1840 accepted as Elliptoideus sloatianus (I. Lea, 1840)
- Species Unio slobodzeanus Bogachev, 1961 †
- Species Unio smaragdina Anton, 1838 accepted as Cristaria plicata (Leach, 1814)
- Species Unio smaragdites W. H. Benson, 1862 accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio smiciklasi Brusina, 1902 † accepted as Unio pavlovici rusani Brusina, 1902 †
- Species Unio smithii J. E. Gray, 1833 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio soboles P. Fischer, 1891 accepted as Lens micropterus (Morelet, 1866)
- Species Unio solandri J. De C. Sowerby, 1826 † accepted as Palindonaia solandri (J. De C. Sowerby, 1826) †
- Species Unio soledadensis Crosse & P. Fischer, 1893 accepted as Nephronaias aztecorum (R. A. Philippi, 1847)
- Species Unio soleilleti Bourguignat, 1885 accepted as Unio dembeae Reeve, 1865
- Species Unio soleniformis I. Lea, 1831 accepted as Margaritifera monodonta (Say, 1829)
- Species Unio solida Anton, 1838 accepted as Chambardia rubens (Lamarck, 1819)
- Species Unio solidulus R. A. Philippi, 1869 accepted as Diplodon solidulus (R. A. Philippi, 1869)
- Species Unio solidus I. Lea, 1838 accepted as Pleurobema sintoxia (Rafinesque, 1820)
- Species Unio solisiana A. d'Orbigny, 1835 accepted as Diplodon solisianus (A. d'Orbigny, 1835)
- Species Unio sophievkaensis Gozhik, 1978 †
- Species Unio sordidis I. Lea, 1852 accepted as Unio sordidus I. Lea, 1852
- Species Unio sordidus I. Lea, 1852 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio sowerbianus I. Lea, 1834 accepted as Epioblasma haysiana (I. Lea, 1834)
- Species Unio spadiceus I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio sparsa K. Martin, 1933 † accepted as Euciroa sparsa (K. Martin, 1933) †
- Species Unio sparsus Küster, 1861 accepted as Rotundaria kleiniana (I. Lea, 1852)
- Species Unio sparsus I. Lea, 1841 accepted as Theliderma sparsa (I. Lea, 1841)
- Species Unio sparus I. Lea, 1868 accepted as Cambarunio jonesii (I. Lea, 1859)
- Species Unio spatulatus I. Lea, 1845 accepted as Venustaconcha ellipsiformis (Conrad, 1836)
- Species Unio specialis Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio speciosus I. Lea, 1862 accepted as Quadrula apiculata (Say, 1829)
- Species Unio sphaericus I. Lea, 1868 accepted as Rotundaria refulgens (I. Lea, 1868)
- Species Unio sphaericus Ionescu-Argetoaia, 1918 † accepted as Psilunio (Cyclopotomida) sphaericus (Ionescu-Argetoaia, 1918) †
- Species Unio spheniopsis Morelet, 1849 accepted as Pachynaias spheniopsis (Morelet, 1849)
- Species Unio sphenorhynchus Crosse & P. Fischer, 1894 accepted as Nephronaias sphenorhyncha (Crosse & P. Fischer, 1894)
- Species Unio spillmanii I. Lea, 1861 accepted as Hamiota perovalis (Conrad, 1834)
- Species Unio spinellii Spinelli, 1852 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio spinosa I. Lea, 1836 accepted as Unio spinosus I. Lea, 1836
- Species Unio spinosus I. Lea, 1836 accepted as Elliptio spinosa (I. Lea, 1836)
- Species Unio spissus I. Lea, 1859 accepted as Elliptio downiei (I. Lea, 1858)
- Species Unio splendens Goldfuss, 1837 † accepted as Anodonta splendens (Goldfuss, 1837) †
- Species Unio spratti Calvert & Neumayr, 1880 † accepted as Unio dardanus var. spratti Calvert & Neumayr, 1880 †
- Species Unio springfieldensis Ludbrook, 1961 † accepted as Prohyria eyrensis (Etheridge, 1892) †
- Species Unio squalidus I. Lea, 1863 accepted as Uniomerus carolinianus (Bosc, 1801)
- Species Unio squameus I. Lea, 1862 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio stabilis I. Lea, 1861 accepted as Pleurobema stabilis (I. Lea, 1861)
- Species Unio stachei Neumayr, 1875 † accepted as Potomida stachei (Neumayr, 1875) †
- Species Unio staffinensis Forbes, 1851 † accepted as Quenstedtia staffinensis (Forbes, 1851) †
- Species Unio stagnalis Conrad, 1849 accepted as Villosa vibex (Conrad, 1834)
- Species Unio stagnorum Dautzenberg, 1890 accepted as Coelatura stagnorum (Dautzenberg, 1890)
- Species Unio stantoni C. A. White, 1907 † accepted as Plesielliptio stantoni (C. A. White, 1907) †
- Species Unio stapes I. Lea, 1831 accepted as Theliderma stapes (I. Lea, 1831)
- Species Unio stefanescoi Tournouër, 1879 † accepted as Ebersininaia stefanescui (Tournouër, 1879) †
- Species Unio stegersbachensis (Sauerzopf, 1952) †
- Species Unio steindachneri Calvert & Neumayr, 1880 † accepted as Unio dardanus var. steindachneri Calvert & Neumayr, 1880 †
- Species Unio stepanoffi Drouët, 1881 accepted as Unio crassus Philipsson, 1788
- Species Unio stephaninii Adami, 1882 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio steveniana Krynicki, 1837
- Species Unio stevenianus Stepanov, 1870 accepted as Unio crassus Philipsson, 1788
- Species Unio stevensii I. Lea, 1871 accepted as Triplodon corrugatus (Lamarck, 1819)
- Species Unio stewardi C. A. White, 1876 † accepted as Epioblasma stewardi (C. A. White, 1876) †
- Species Unio stewardsonii I. Lea, 1852 accepted as Epioblasma stewardsonii (I. Lea, 1852)
- Species Unio stojadinovici Milošević, 1968 †
- Species Unio stolatus E. von Martens, 1900 accepted as Prohyriopsis stolata (E. von Martens, 1900)
- Species Unio stoliczkai Neumayr, 1875 † accepted as Psilunio (Psilunio) stoliczkai (Neumayr, 1875) †
- Species Unio stonensis I. Lea, 1840 accepted as Eurynia dilatata (Rafinesque, 1820)
- Species Unio stramineus Conrad, 1834 accepted as Lampsilis straminea (Conrad, 1834)
- Species Unio strebelii I. Lea, 1866 accepted as Nephronaias aztecorum (R. A. Philippi, 1847)
- Species Unio striatissimus J. G. Anthony, 1865 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio striatulus I. Lea, 1857 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio striatus I. Lea, 1840 accepted as Pleurobema pyriforme (I. Lea, 1857)
- Species Unio striatus Münster, 1837 † accepted as Panopaea striata (Münster, 1837) †
- Species Unio strictiplicatus Noulet, 1864 † accepted as Margaritifera (Pseudunio) flabellata (Goldfuss, 1837) †
- Species Unio strigosus I. Lea, 1840 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio strobeli Bourguignat, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio strodeanus B. H. Wright, 1898 accepted as Pleurobema strodeanum (B. H. Wright, 1898)
- Species Unio strossmayerianus Brusina, 1874 † accepted as Potomida strossmayeriana (Brusina, 1874) †
- Species Unio strumosus I. Lea, 1872 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio stuhlmanni E. von Martens, 1897 accepted as Coelatura stuhlmanni (E. von Martens, 1897)
- Species Unio stungtrangensis Fischer & Dautzenberg, 1904 accepted as Hyriopsis myersiana (I. Lea, 1856)
- Species Unio sturi M. Hörnes, 1864 † accepted as Bogatschevia sturi (M. Hörnes, 1864) †
- Species Unio sturzae Cobălcescu, 1883 † accepted as Jazkoa sturzae (Cobălcescu, 1883) †
- Species Unio suavidicus I. Lea, 1856 accepted as Diplodon suavidicus (I. Lea, 1856)
- Species Unio subamnicus Locard, 1889 accepted as Unio crassus Philipsson, 1788
- Species Unio subangulatus I. Lea, 1840 accepted as Hamiota subangulata (I. Lea, 1840)
- Species Unio subatavoides Pavlović, 1931 †
- Species Unio subatavus Teisseyre, 1907 † accepted as Teisseyrinaia subatava (Teisseyre, 1907) †
- Species Unio subbatavus Kobelt, 1912 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio subbugensis (Gozhik, 1978) †
- Species Unio subclivosus Teisseyre, 1911 † accepted as Potomida subclivosa (Teisseyre, 1911) †
- Species Unio subconstrictus J. Sowerby, 1813 † accepted as Carbonicola subconstricta (J. Sowerby, 1813) †
- Species Unio subcrassus G. I. Popov, 1968 †
- Species Unio subcroceus Conrad, 1854 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio subcylindraceus I. Lea, 1874 accepted as Elliptio angustata (I. Lea, 1831)
- Species Unio subcylindricus Drouët, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio subdactylinus Martinson, 1951 † accepted as Nodularia subdactylina (Martinson, 1951) †
- Species Unio subdoljiensis Pavlov, 1925 † accepted as Iridea subdoljiensis (Pavlov, 1925) †
- Species Unio subellipsis I. Lea, 1857 accepted as Villosa lienosa (Conrad, 1834)
- Species Unio subellipticus Lindholm, 1932 † accepted as Betekeia subelliptica (Lindholm, 1932) †
- Species Unio subexquisitus Jatsko, 1972 † accepted as Heterunio subexquisitus (Jatsko, 1972) †
- Species Unio subflabellatiformis Jatsko, 1972 †
- Species Unio subflavus I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio subgibbosus I. Lea, 1857 accepted as Elliptio arca (Conrad, 1834)
- Species Unio subglobatus I. Lea, 1871 accepted as Pleuronaia dolabelloides (I. Lea, 1840)
- Species Unio subglobosus I. Lea, 1834 accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio subhoernesi Sinzov, 1897 † accepted as Sinzowinaia subhoernesi (Sinzov, 1897) †
- Species Unio subinflatus (Conrad, 1835) accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio sublatus I. Lea, 1857 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio sublenticularis Teisseyre, 1911 †
- Species Unio subluridus C. T. Simpson, 1892 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio submactraeformis Martinson, 1951 †
- Species Unio submoldavicus B.-Y. Huang & J.-M. Wei, 1976 †
- Species Unio subnicopolis (Gozhik, 1978) †
- Species Unio subniger I. Lea, 1857 accepted as Elliptio fumata (I. Lea, 1857)
- Species Unio subolivaceus I. Lea, 1874 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio suborbicularis Drouët, 1888 accepted as Unio mancus Lamarck, 1819
- Species Unio suborbiculata Lamarck, 1819 accepted as Glebula rotundata (Lamarck, 1819)
- Species Unio subovalis Cornuel, 1874 †
- Species Unio subovatus I. Lea, 1831 accepted as Lampsilis cardium Rafinesque, 1820
- Species Unio subparallela S. V. Wood, 1864 † accepted as Unio subparallelus S. V. Wood, 1864 †
- Species Unio subparallelus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio subparallelus B.-Y. Huang & J.-M. Wei, 1976 †
- Species Unio subparallelus S. V. Wood, 1864 †
- Species Unio subpartschi Laskarev, 1908 †
- Species Unio subpartschi Bogachev, 1936 †
- Species Unio subplanatus Lindholm, 1932 †
- Species Unio subplanatus C. T. Simpson, 1896 † accepted as Rhipidodonta subplanata (C. T. Simpson, 1896) †
- Species Unio subplanus Conrad, 1837 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio subponticus Jatsko, 1954 † accepted as Psilunio subponticus (Jatsko, 1954) †
- Species Unio subporrectus F. A. Roemer, 1836 †
- Species Unio subprimaevis Dyer, 1930 † accepted as Theliderma subprimaevis (Dyer, 1930) †
- Species Unio subprominulus Teisseyre, 1911 †
- Species Unio subradiatodentatus Jatsko, 1954 † accepted as Cuneopsis subradiatodentata (Jatsko, 1954) †
- Species Unio subrectangularis Blanckenhorn, 1927 † accepted as Potomida subrectangularis (Blanckenhorn, 1927) †
- Species Unio subrecurvus Teisseyre, 1907 † accepted as Psilunio (Psilunio) subrecurvus (Teisseyre, 1907) †
- Species Unio subrobustus Servain, 1886 accepted as Unio crassus Philipsson, 1788
- Species Unio subrostratus Say, 1831 accepted as Sagittunio subrostratus (Say, 1831)
- Species Unio subrotundoides I. Lea, 1868 † accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio subrotundus I. Lea, 1831 accepted as Fusconaia subrotunda (I. Lea, 1831)
- Species Unio subrugosa Matheron, 1843 † accepted as Unio subrugosus (Matheron, 1843) †
- Species Unio subrugosus (Matheron, 1843) †
- Species Unio subrumanus Teisseyre, 1911 †
- Species Unio subsciphicus Gozhik, 1978 †
- Species Unio subsinuatus F. C. L. Koch & Dunker, 1837 †
- Species Unio subspatulata Meek & Hayden, 1857 † accepted as Plesielliptio subspatulatus (Meek & Hayden, 1857) †
- Species Unio subspatulatus Meek & Hayden, 1857 † accepted as Plesielliptio subspatulatus (Meek & Hayden, 1857) †
- Species Unio subsquamosus I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio substriatus I. Lea, 1856 accepted as Indonaia substriata (I. Lea, 1856)
- Species Unio subtentus Say, 1825 accepted as Ptychobranchus subtentus (Say, 1825)
- Species Unio subteritus (Say, 1825) accepted as Ptychobranchus subtentus (Say, 1825)
- Species Unio subtetragonus Michaud, 1831 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio subthalassinus Penecke, 1883 † accepted as Unio thalassinus Brusina, 1874 †
- Species Unio subtigridis Locard, 1883 accepted as Unio delicatus I. Lea, 1863
- Species Unio subtilis Drouët, 1879 accepted as Unio crassus Philipsson, 1788
- Species Unio subtontus Say, 1825 accepted as Ptychobranchus subtentus (Say, 1825)
- Species Unio subtrapezius R. A. Philippi, 1847 accepted as Mya variabilis Maton, 1811
- Species Unio subtrapezoidalis Q.-H. Ma, 1976 †
- Species Unio subtriatus accepted as Unio substriatus I. Lea, 1856
- Species Unio subtrigonalis Whitfield, 1907 † accepted as Callonaia subtrigonalis (Whitfield, 1907) †
- Species Unio subtrigonus Noulet, 1864 † accepted as Margaritifera (Pseudunio) flabellata (Goldfuss, 1837) †
- Species Unio subtrigonus G. B. Sowerby II, 1867 accepted as Pseudodon vagulus (P. Fischer, 1891)
- Species Unio subtruncatosus Cossmann, 1908 †
- Species Unio subtruncatus J. De C. Sowerby, 1836 †
- Species Unio subtumidus A. d'Orbigny, 1850 † accepted as Parreysia subtumida (A. d'Orbigny, 1850) †
- Species Unio subundulatus X.-Z. Liu, 1984 †
- Species Unio subviridis Conrad, 1835 accepted as Lasmigona subviridis (Conrad, 1835)
- Species Unio subyirijinxiensis X.-Z. Liu, 1988 †
- Species Unio succineus Drouët, 1881 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio succissus I. Lea, 1852 accepted as Cyclonaias succissa (I. Lea, 1852)
- Species Unio sudovskii [sic] † accepted as Unio sudovskyi Andrusov, 1906 †
- Species Unio sudovskyi Andrusov, 1906 †
- Species Unio sudus I. Lea, 1857 accepted as Villosa vibex (Conrad, 1834)
- Species Unio sula C. T. Simpson, 1900 accepted as Gibbosula laosensis (I. Lea, 1863)
- Species Unio sulcatus I. Lea, 1829 accepted as Epioblasma obliquata (Rafinesque, 1820)
- Species Unio sulcidens Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio sumatrensis I. Lea, 1859 accepted as Lens contradens (I. Lea, 1838)
- Species Unio sumatrensis Dunker, 1852 accepted as Rectidens sumatrensis (Dunker, 1852)
- Species Unio suni M.-C. Chow, 1953 † accepted as Unionelloides suni (M.-C. Chow, 1953) †
- Species Unio supenawensis Stanton & Hatcher, 1905 † accepted as Quadrula supenawensis (Stanton & Hatcher, 1905) †
- Species Unio superbus I. Lea, 1843 accepted as Physunio superbus (I. Lea, 1843)
- Species Unio superiorensis W. A. Marsh, 1897 accepted as Lampsilis siliquoidea (Barnes, 1823)
- Species Unio superstes Neumayr, 1899 accepted as Rhombuniopsis superstes (Neumayr, 1899)
- Species Unio supragibbosus Whiteaves, 1885 † accepted as Plesielliptio supragibbosus (Whiteaves, 1885) †
- Species Unio suprajurensis F. A. Roemer, 1839 † accepted as Astarte suprajurensis (F. A. Roemer, 1839) †
- Species Unio suskalovici Pavlović, 1931 †
- Species Unio suspiciosus Bogachev, 1908 †
- Species Unio sutrangensis Morlet, 1889 accepted as Hyriopsis myersiana (I. Lea, 1856)
- Species Unio suttoni B. H. Wright, 1897 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio swainsoni G. B. Sowerby II, 1868 accepted as Alasmidonta undulata (Say, 1817)
- Species Unio swananoensis Hanley, 1843 accepted as Alasmidonta raveneliana (I. Lea, 1834)
- Species Unio swinhoei G. B. Sowerby II, 1866
- Species Unio swinhoei H. Adams, 1866 accepted as Pletholophus tenuis (J. E. Gray, 1833)
- Species Unio swordianus S. H. Wright, 1897 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio symmetricus I. Lea, 1845 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio syriacus I. Lea, 1863 accepted as Unio damascensis I. Lea, 1863
- Species Unio szechenyii Neumayr, 1898 accepted as Cuneopsis szechenyii (Neumayr, 1899)
- Species Unio szegedensis Halaváts, 1891 † accepted as Unio crassus Philipsson, 1788
- Species Unio tabascoensis Küster, 1856 accepted as Nephronaias tabascoensis (Küster, 1856)
- Species Unio taeniatus Conrad, 1834 accepted as Villosa taeniata (Conrad, 1834)
- Species Unio tahetianus (I. Lea, 1834) accepted as Pleurobema taitianum (I. Lea, 1834)
- Species Unio taitianus I. Lea, 1834 accepted as Pleurobema taitianum (I. Lea, 1834)
- Species Unio talandi T. Fuchs, 1877 †
- Species Unio tamanensis Bogachev, 1961 † accepted as Bogatschevia tamanensis (Bogachev, 1961) †
- Species Unio tamaulipasensis Crosse & P. Fischer, 1894 accepted as Sphenonaias taumilapana (Conrad, 1855)
- Species Unio tammouziana Pallary, 1939 accepted as Unio tigridis Bourguignat, 1852
- Species Unio tampicoensis I. Lea, 1838 accepted as Cyrtonaias tampicoensis (I. Lea, 1838)
- Species Unio tanganyicensis E. A. Smith, 1880 accepted as Grandidieria burtoni (S. P. Woodward, 1859)
- Species Unio tanphilievi Mangikian, 1929 †
- Species Unio tappanianus I. Lea, 1838 accepted as Lasmigona subviridis (Conrad, 1835)
- Species Unio taumilapanus Conrad, 1855 accepted as Sphenonaias taumilapana (Conrad, 1855)
- Species Unio tavoyensis A. Gould, 1843 accepted as Leoparreysia tavoyensis (A. Gould, 1843)
- Species Unio tecomatensis I. Lea, 1841 accepted as Cyrtonaias tampicoensis (I. Lea, 1838)
- Species Unio tecomensis (I. Lea, 1841) accepted as Cyrtonaias tampicoensis (I. Lea, 1838)
- Species Unio tehuantepecensis Crosse & P. Fischer, 1894 accepted as Popenaias tehuantepecensis (Crosse & P. Fischer, 1894)
- Species Unio tellicoensis I. Lea, 1872 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio tellinarius Goldfuss, 1837 † accepted as Carbonicola acuta (J. Sowerby, 1813) †
- Species Unio tellinoides (J. Hall, 1845) † accepted as Ligumia tellinoides (J. Hall, 1845) †
- Species Unio tenebricus I. Lea, 1857 accepted as Villosa umbrans (I. Lea, 1857)
- Species Unio tenebrosus Conrad, 1834 accepted as Lampsilis radiata (Gmelin, 1791)
- Species Unio tener I. Lea, 1840 accepted as Villosa iris (I. Lea, 1829)
- Species Unio tenerus C. T. Simpson, 1892 accepted as Villosa delumbis (Conrad, 1834)
- Species Unio tennesseensis I. Lea, 1840 accepted as Cambarunio taeniatus pictus (I. Lea, 1834)
- Species Unio tenuis J. E. Gray, 1833 accepted as Pletholophus tenuis (J. E. Gray, 1833)
- Species Unio tenuisculus Frierson, 1911 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio tenuissimus (I. Lea, 1829) accepted as Leptodea leptodon (Rafinesque, 1820)
- Species Unio teretiusculus R. A. Philippi, 1847 accepted as Nitia teretiuscula (R. A. Philippi, 1847)
- Species Unio terminalis Bourguignat, 1852
- Species Unio terraerubrae Meek, 1875 † accepted as Antediplodon terraerubrae (Meek, 1875) †
- Species Unio tertius Bogachev, 1961 †
- Species Unio tesserulae I. Lea, 1862 accepted as Pleurobema oviforme (Conrad, 1834)
- Species Unio testudineus Morelet, 1849 accepted as Psoronaias semigranosa (R. A. Philippi, 1843)
- Species Unio tetralasmus Say, 1831 accepted as Uniomerus tetralasmus (Say, 1831)
- Species Unio tetricus I. Lea, 1857 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio texasensis "Lea, 1860" accepted as Unio texasiensis I. Lea, 1857
- Species Unio texasiensis I. Lea, 1857 accepted as Toxolasma texasiense (I. Lea, 1857)
- Species Unio thaiensis T. Habe, 1964 accepted as Lens contradens (I. Lea, 1838)
- Species Unio thailandica Hayami, 1968 † accepted as Eocuneopsis thailandica (Hayami, 1968) †
- Species Unio thalassinus Brusina, 1874 †
- Species Unio theca W. H. Benson, 1862 accepted as Lamellidens corrianus (I. Lea, 1834)
- Species Unio thermalis Drouët, 1896 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio thiesseae Drouët, 1892 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio thomasi J. Henderson, 1934 † accepted as Antediplodon thomasi (J. Henderson, 1934) †
- Species Unio thomsoni E. A. Smith, 1880 accepted as Grandidieria burtoni (S. P. Woodward, 1859)
- Species Unio thorntonii I. Lea, 1857 accepted as Pleuronaia dolabelloides (I. Lea, 1840)
- Species Unio thospiensis Kobelt, 1915 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio thulei F. R. Woodward, 1971 †
- Species Unio thuringensis Ludwig, 1861 † accepted as Anthracosia thuringensis (Ludwig, 1861) †
- Species Unio thwaitesii I. Lea, 1860 accepted as Lamellidens marginalis (Lamarck, 1819)
- Species Unio thwaitsii I. Lea, 1859 accepted as Lamellidens marginalis (Lamarck, 1819)
- Species Unio tianshanensis B.-Y. Huang & J.-M. Wei, 1976 †
- Species Unio tiberiadensis Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio tientsinensis Crosse & Debeaux, 1863 accepted as Aculamprotula tientsinensis (Crosse & Debeaux, 1863)
- Species Unio tifleticus Pallary, 1923 accepted as Unio gibbus Spengler, 1793
- Species Unio tigridis Bourguignat, 1852
- Species Unio tigris Pallary, 1939 accepted as Unio tigridis Bourguignat, 1852
- Species Unio tiguricus Servain, 1886 accepted as Unio crassus Philipsson, 1788
- Species Unio timius Locard, 1883 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio tinctus Drouët, 1893 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio tinkeri B. H. Wright, 1899 accepted as Obovaria unicolor (I. Lea, 1845)
- Species Unio tiraspolitanus Chepalyga, 1967 †
- Species Unio todorovici Pavlović, 1931 †
- Species Unio tomiensis Lebedev, 1959 †
- Species Unio tomislavi Brusina, 1902 † accepted as Potomida zelebori (M. Hörnes, 1864) †
- Species Unio tommasii Adami, 1886 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio topekaensis I. Lea, 1868 accepted as Ligumia subrostrata (Say, 1831)
- Species Unio torreyensis M. A. Hanna, 1927 † accepted as Panopea torreyensis (M. A. Hanna, 1927) †
- Species Unio tortivus I. Lea, 1840 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio tortuosus G. B. Sowerby II, 1868 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio tortuosus I. Lea, 1865 accepted as Aculamprotula tortuosa (I. Lea, 1865)
- Species Unio toulouzanii Matheron, 1843 †
- Species Unio tournali Matheron, 1879 † accepted as Palindonaia tournali (Matheron, 1879) †
- Species Unio tournoueri Pallary, 1901 †
- Species Unio toxonotus C. A. White, 1886 † accepted as Lampsilis toxonotus (C. A. White, 1886) †
- Species Unio trabalis Conrad, 1834 accepted as Villosa trabalis (Conrad, 1834)
- Species Unio tracheae Kobelt & Rolle, 1895 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio trajani "Mikhaylovskiy, 1909" † accepted as Pseudunio flabellatiformis (Grigorovich-Beresovskiy, 1915) †
- Species Unio transbaicalensis Martinson, 1961 †
- Species Unio transcarpaticus Teisseyre, 1907 † accepted as Pristinunio transcarpaticus (Teisseyre, 1907) †
- Species Unio transpacifica Arnold & Hannibal, 1912 † accepted as Plesielliptio transpacificus (Arnold & Hannibal, 1912) †
- Species Unio transpacificus Arnold & Hannibal, 1912 † accepted as Plesielliptio transpacificus (Arnold & Hannibal, 1912) †
- Species Unio transrhyphaeus Bogachev, 1924 † accepted as Nodularia transrhyphaea (Bogachev, 1924) †
- Species Unio transversalis de Serres, 1853 †
- Species Unio transversus (T. Brown, 1843) † accepted as Carbonicola acuta (J. Sowerby, 1813) †
- Species Unio trapezoides I. Lea, 1831 accepted as Plectomerus dombeyanus (Valenciennes, 1827)
- Species Unio trapezoideus (Gozhik, 2006) †
- Species Unio traversii Pollonera, 1888 accepted as Unio dembeae Reeve, 1865
- Species Unio triangularis Barnes, 1823 accepted as Epioblasma triquetra (Rafinesque, 1820)
- Species Unio triangularis Macarovici, 1940 † accepted as Betekeia triangularis (Macarovici, 1940) †
- Species Unio triclavus Heude, 1877 accepted as Lamprotula triclava (Heude, 1877)
- Species Unio triclivosus Teisseyre, 1911 †
- Species Unio tricolor Küster, 1856
- Species Unio triembolus W. H. Benson, 1862 accepted as Parreysia nagpoorensis (I. Lea, 1860)
- Species Unio trifidus accepted as Diplodon parallelopipedon (I. Lea, 1834)
- Species Unio triformis Heude, 1877 accepted as Lanceolaria triformis (Heude, 1877)
- Species Unio trigoniaformis Maury, 1902 † accepted as Amblema trigoniaformis (Maury, 1902) †
- Species Unio trigonus I. Lea, 1831 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio trigonus F. A. Roemer, 1836 † accepted as Cardinia listeri (J. Sowerby, 1817) †
- Species Unio trinacrus I. Lea, 1861 accepted as Ptychobranchus foremanianus (I. Lea, 1842)
- Species Unio trinilensis E. Dubois, 1908 † accepted as Pseudodon vondembuschianus trinilensis (E. Dubois, 1908) †
- Species Unio tripartitus I. Lea, 1863 accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio tripolitanus Bourguignat, 1852 accepted as Leguminaia saulcyi (Bourguignat, 1852)
- Species Unio trirostris G. B. Sowerby II, 1868
- Species Unio trirostris Hanley, 1863 accepted as Parreysia nagpoorensis (I. Lea, 1860)
- Species Unio tristis Morelet, 1845 accepted as Margaritifera (Margaritifera) margaritifera (Linnaeus, 1758)
- Species Unio tristrami Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio trisulcatus Heude, 1883 accepted as Acuticosta trisulcata (Heude, 1883)
- Species Unio triumphans B. H. Wright, 1898 accepted as Megalonaias nervosa (Rafinesque, 1820)
- Species Unio trompi Drouët & Chaper, 1892 accepted as Elongaria trompi (Drouët & Chaper, 1892)
- Species Unio troostensis I. Lea, 1834 accepted as Venustaconcha troostensis (I. Lea, 1834)
- Species Unio troostii I. Lea, 1867 accepted as Unio troostensis I. Lea, 1834
- Species Unio troschelianus I. Lea, 1852 accepted as Pleurobema georgianum (I. Lea, 1841)
- Species Unio trosculus I. Lea, 1843 accepted as Unio trossulus I. Lea, 1843
- Species Unio trossulus I. Lea, 1843 accepted as Villosa amygdalum (I. Lea, 1843)
- Species Unio truncatissima Mich. †
- Species Unio truncatosa Michaud, 1837 † accepted as Palindonaia truncatosa (Michaud, 1837) †
- Species Unio tryoni B. H. Wright, 1888 accepted as Elliptio jayensis (I. Lea, 1838)
- Species Unio tschiliensis Sturany, 1902 † accepted as Cuneopsis tschiliensis (Sturany, 1902) †
- Species Unio tschulymensis [sic] † accepted as Proarcidopsis chulymensis (Lebedev, 1958) †
- Species Unio tsentahozensis Yakushina, 1973 †
- Species Unio tuberculatus Barnes, 1823 accepted as Tritogonia verrucosa (Rafinesque, 1820)
- Species Unio tuberosus I. Lea, 1840 accepted as Theliderma metanevra (Rafinesque, 1820)
- Species Unio tuchiasanus L. S. Russell, 1932 † accepted as Fusconaia tuchiasana (L. S. Russell, 1932) †
- Species Unio tudagouensis Yakushina, 1964 †
- Species Unio tumescens I. Lea, 1845 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio tumescens S. V. Wood, 1864 † accepted as Unio gibbsii Forbes, 1856 †
- Species Unio tumida J. De C. Sowerby, 1840 † accepted as Parreysia subtumida (A. d'Orbigny, 1850) †
- Species Unio tumidiformis Lindholm, 1932 accepted as Heterunio tumidiformis (Lindholm, 1932) †
- Species Unio tumidiformis Castro, 1885
- Species Unio tumidulus I. Lea, 1856 accepted as Lens contradens (I. Lea, 1838)
- Species Unio tumidus Philipsson, 1788
- Species Unio tungusicus Bogachev, 1963 †
- Species Unio tuomeyi I. Lea, 1852 accepted as Elliptio cylindracea Frierson, 1927
- Species Unio tuositaiensis B.-Y. Huang & J.-M. Wei, 1976 †
- Species Unio turcicus Küster, 1862 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio turgaicus Bogachev, 1961 †
- Species Unio turgidula Cornuel, 1874 †
- Species Unio turgidulus I. Lea, 1858 accepted as Epioblasma turgidula (I. Lea, 1858)
- Species Unio turgidus I. Lea, 1838 accepted as Rotundaria pustulosa (I. Lea, 1831)
- Species Unio turgidus (T. Brown, 1843) † accepted as Anthracosphaerium turgidum (T. Brown, 1843) †
- Species Unio turicus Servain, 1886 accepted as Unio crassus Philipsson, 1788
- Species Unio turtonii Payraudeau, 1826 accepted as Unio mancus turtonii Payraudeau, 1826
- Species Unio tuscumbiensis I. Lea, 1871 accepted as Fusconaia cuneolus (I. Lea, 1840)
- Species Unio tuzakeniegouensis J.-M. Wei, 1984 †
- Species Unio tyjensis Lebedev, 1958 †
- Species Unio tyrrelli L. S. Russell, 1931 † accepted as Plesielliptio brachyopisthus (C. A. White, 1876) †
- Species Unio uber Conrad, 1866 accepted as Obovaria unicolor (I. Lea, 1845)
- Species Unio ucrainicus Jatsko, 1955 † accepted as Pseudunio ucrainicus (Jatsko, 1955) †
- Species Unio uhareensis I. Lea, 1868 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio ullerichi Modell, 1950 †
- Species Unio umbonarius Wolff, 1897 † accepted as Psilunio flexicostatus (Gümbel, 1861) †
- Species Unio umbonatus Eichwald, 1861 † accepted as Palaeomutela umbonata (Eichwald, 1861) †
- Species Unio umbrans I. Lea, 1857 accepted as Villosa umbrans (I. Lea, 1857)
- Species Unio umbrosus I. Lea, 1856 accepted as Cyrtonaias umbrosa (I. Lea, 1856)
- Species Unio umbrosus I. Lea, 1857 accepted as Unio umbrans I. Lea, 1857
- Species Unio undatus Barnes, 1823 accepted as Fusconaia flava (Rafinesque, 1820)
- Species Unio undulata Say, 1817 accepted as Alasmidonta undulata (Say, 1817)
- Species Unio undulatum J.-S. Yu, G.-Y. Dong & P.-Y. Yao, 1989 †
- Species Unio undulatus Barnes, 1823 accepted as Amblema plicata (Say, 1817)
- Species Unio unduliferus Küster, 1861 accepted as Potomida littoralis (Cuvier, 1798)
- Species Unio unicolor I. Lea, 1845 accepted as Obovaria unicolor (I. Lea, 1845)
- Species Unio unicostatus B. H. Wright, 1899 accepted as Leaunio lienosus unicostatus (B. H. Wright, 1899)
- Species Unio uniformis J. Sowerby, 1813 † accepted as Pleuromya uniformis (J. Sowerby, 1813) †
- Species Unio upsonii W. A. Marsh, 1887 accepted as Ortmanniana ligamentina (Lamarck, 1819)
- Species Unio uralensis B. I. Chernyshev, 1937 †
- Species Unio urii J. Fleming, 1828 †
- Species Unio urjupiensis Lebedev, 1958 †
- Species Unio uruguayensis I. Lea, 1860 accepted as Diplodon uruguayensis (I. Lea, 1860)
- Species Unio uryuensis K. Suzuki, 1941 †
- Species Unio uschcalcensis Jatsko, 1955 †
- Species Unio usumasintae Crosse & P. Fischer, 1893 accepted as Psoronaias usumasintae (Crosse & P. Fischer, 1893)
- Species Unio utratus Goldfuss, 1837 † accepted as Carbonicola aquilina (J. De C. Sowerby, 1840) †
- Species Unio utriculus I. Lea, 1845 accepted as Fusconaia masoni (Conrad, 1834)
- Species Unio uzbekistanica Repman, 1963 † accepted as Unio uzbekistanicus Repman, 1963 †
- Species Unio uzbekistanicus Repman, 1963 †
- Species Unio vaalensis Chaper, 1885 accepted as Cafferia caffra (Krauss, 1848)
- Species Unio vagulus P. Fischer, 1891 accepted as Pseudodon vagulus (P. Fischer, 1891)
- Species Unio valdensis Mantell, 1844 † accepted as Margaritifera valdensis (Mantell, 1844) †
- Species Unio valdivianus R. A. Philippi, 1869 accepted as Diplodon chilensis (J. E. Gray, 1828)
- Species Unio valentianus G. B. Sowerby II, 1866
- Species Unio valentinus Rossmässler, 1854 accepted as Unio mancus Lamarck, 1819
- Species Unio validus I. Lea, 1871 accepted as Pleuronaia barnesiana (I. Lea, 1838)
- Species Unio vallatus I. Lea, 1868 accepted as Rotundaria asperata (I. Lea, 1861)
- Species Unio vanuxemensis I. Lea, 1838 accepted as Villosa vanuxemensis (I. Lea, 1838)
- Species Unio vanuxemii I. Lea, 1867 accepted as Unio vanuxemensis I. Lea, 1838
- Species Unio vardinicus Fontannes, 1883 †
- Species Unio varicosa Lamarck, 1819 accepted as Alasmidonta varicosa (Lamarck, 1819)
- Species Unio varicosus I. Lea, 1831 accepted as Plethobasus cicatricosus (Say, 1829)
- Species Unio vasarhelyi [sic] † accepted as Unio vasarhelyii Lörenthey, 1902 †
- Species Unio vasarhelyii Lörenthey, 1902 †
- Species Unio vaughanianus I. Lea, 1838 accepted as Villosa vaughaniana (I. Lea, 1838)
- Species Unio vectensis S. V. Wood, 1864 † accepted as Modellinaia vectensis (S. V. Wood, 1864) †
- Species Unio veillanicus Bourguignat, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio velaris Hanley, 1856 accepted as Physunio superbus (I. Lea, 1843)
- Species Unio velatus Conrad, 1854 accepted as Ptychobranchus foremanianus (I. Lea, 1842)
- Species Unio vellicatus Reeve, 1865 accepted as Nephronaias ravistella (Morelet, 1849)
- Species Unio velthuizeni Schepman, 1896 accepted as Hyriopsis velthuizeni (Schepman, 1896)
- Species Unio velum Say, 1829 accepted as Leptodea leptodon (Rafinesque, 1820)
- Species Unio venerius Fontannes, 1880 †
- Species Unio ventricosa Cornuel, 1874 †
- Species Unio ventricosus Barnes, 1823 accepted as Lampsilis cardium Rafinesque, 1820
- Species Unio venustus I. Lea, 1838 accepted as Venustaconcha ellipsiformis (Conrad, 1836)
- Species Unio venustus Morelet, 1866 accepted as Scabies scobinatus (I. Lea, 1856)
- Species Unio veracruzensis I. Lea, 1868 accepted as Cyrtonaias umbrosa (I. Lea, 1856)
- Species Unio veraepacis Tristram, 1863 accepted as Popenaias popeii (I. Lea, 1857)
- Species Unio verbanicus Bourguignat, 1883 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio verbecki E. von Martens, 1897 accepted as Lens contradens (I. Lea, 1838)
- Species Unio verecundus A. Gould, 1850 accepted as Simpsonella purpurea (Valenciennes, 1827)
- Species Unio verrauxi Küster, 1856 accepted as Unio caffer verrauxi Küster, 1856
- Species Unio verreauianus I. Lea, 1856 accepted as Unio caffer Krauss, 1848
- Species Unio verreauxianus I. Lea, 1867 accepted as Unio verreauianus I. Lea, 1856
- Species Unio verrucifer E. von Martens, 1894 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio verrucosa Barnes, 1823 accepted as Unio verrucosus Barnes, 1823
- Species Unio verrucosa Valennciennes, 1827
- Species Unio verrucosiformis Whitfield, 1903 † accepted as Proparreysia verrucosiformis (Whitfield, 1903) †
- Species Unio verrucosus Barnes, 1823 accepted as Rotundaria tuberculata (Rafinesque, 1820)
- Species Unio verus I. Lea, 1861 accepted as Pleurobema verum (I. Lea, 1861)
- Species Unio verutus I. Lea, 1859 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio vescoi Bourguignat, 1856 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio vesicularis I. Lea, 1872 accepted as Villosa amygdalum (I. Lea, 1843)
- Species Unio vestitoides Martinson, 1951 † accepted as Acuticosta vestitoides (Martinson, 1951) †
- Species Unio vestitus I. Lea, 1862 accepted as Elliptio congaraea (I. Lea, 1831)
- Species Unio vetusta Meek, 1860 † accepted as Plesielliptio vetustus (Meek, 1860) †
- Species Unio vetustus Meek, 1860 † accepted as Plesielliptio vetustus (Meek, 1860) †
- Species Unio veziani Choffat, 1885 †
- Species Unio vibex Conrad, 1834 accepted as Villosa vibex (Conrad, 1834)
- Species Unio vicarius Westerlund, 1879
- Species Unio vicaryi Blanford, 1883 † accepted as Indobaphia vicaryi (Blanford, 1883) †
- Species Unio vicentei Bataller, 1947 †
- Species Unio vicinus I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio vicinus Preston, 1910 accepted as Unio silongweensis Preston, 1912
- Species Unio villosus B. H. Wright, 1898 accepted as Villosa villosa (B. H. Wright, 1898)
- Species Unio vinckei Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio violaceus Spengler, 1793 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio viquesneli Pavlović, 1931 †
- Species Unio virens I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio virescens I. Lea, 1858 accepted as Lampsilis virescens (I. Lea, 1858)
- Species Unio virginiana Lamarck, 1819 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio viridans I. Lea, 1859 accepted as Elliptio arctata (Conrad, 1834)
- Species Unio viridicatus I. Lea, 1857 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio viridiflavus Küster, 1854 accepted as Unio elongatulus C. Pfeiffer, 1825
- Species Unio viridiradiatus I. Lea, 1859 accepted as Elliptio pullata (I. Lea, 1857)
- Species Unio viridis Ludwig, 1861 † accepted as Unio tumidus ludwigi Wenz, 1922 †
- Species Unio viridulus I. Lea, 1863 accepted as Elliptio lanceolata (I. Lea, 1827)
- Species Unio visseri Bourguignat, 1886 accepted as Coelatura horei (E. A. Smith, 1880)
- Species Unio vittatus I. Lea, 1859 accepted as Velesunio ambiguus (R. A. Philippi, 1847)
- Species Unio vodnoensis Pavlović, 1931 †
- Species Unio vogti Locard, 1893 † accepted as Ptychorhynchoideus vogti (Locard, 1893) †
- Species Unio voltzii F. C. L. Koch & Dunker, 1837 † accepted as Unio subsinuatus F. C. L. Koch & Dunker, 1837 †
- Species Unio voltzii Kobelt, 1911 accepted as Unio pictorum (Linnaeus, 1758)
- Species Unio vonbuschea G. B. Sowerby II, 1866 accepted as Pseudodon vondembuschianus (I. Lea, 1840)
- Species Unio vukasovicianus Brusina, 1874 † accepted as Potomida vukasoviciana (Brusina, 1874) †
- Species Unio vukotinovici M. Hörnes, 1864 † accepted as Potomida vukotinovici (M. Hörnes, 1864) †
- Species Unio vulcanus Hanley, 1876 accepted as Leoparreysia vulcanus (Hanley, 1876)
- Species Unio waccamawensis I. Lea, 1863 accepted as Elliptio waccamawensis (I. Lea, 1863)
- Species Unio wagneri Kobelt & Rolle, 1895 accepted as Potomida semirugata (Lamarck, 1819)
- Species Unio waikarensis Colenso, 1844 accepted as Echyridella menziesii (J. E. Gray, 1843)
- Species Unio walkeri B. H. Wright, 1897 accepted as Medionidus walkeri (B. H. Wright, 1897)
- Species Unio waltoni B. H. Wright, 1888 accepted as Elliptio ahenea (I. Lea, 1843)
- Species Unio waqianensis X.-Z. Liu, 1988 †
- Species Unio wardii I. Lea, 1862 accepted as Theliderma metanevra (Rafinesque, 1820)
- Species Unio wasatchensis T. D. A. Cockerell, 1914 † accepted as Plesielliptio wasatchensis (T. D. A. Cockerell, 1914) †
- Species Unio wasawensis X.-Z. Liu, 1988 †
- Species Unio washakiensis Meek, 1871 † accepted as Elliptio washakiensis (Meek, 1871) †
- Species Unio wateleti Deshayes, 1860 † accepted as Palindonaia wateleti (Deshayes, 1860) †
- Species Unio wayaopuensis B.-P. Liu & Z.-S. Li, 1980 †
- Species Unio websterii B. H. Wright, 1888 accepted as Elliptio monroensis (I. Lea, 1843)
- Species Unio weithoferi Modell, 1931 † accepted as Rhombuniopsis weithoferi (Modell, 1931) †
- Species Unio weiyuanensis X.-Z. Liu, 1984 †
- Species Unio weiyuanensis S.-Y. Cai, 1986 †
- Species Unio weldonensis I. Lea, 1863 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio wendli Modell, 1931 †
- Species Unio wenzii Kobelt, 1915 accepted as Unio bruguierianus Bourguignat, 1853
- Species Unio wershutski Popova, 1964 † accepted as Tchangsinaia wershutski (Popova, 1964) †
- Species Unio wetzleri (Dunker, 1848) † accepted as Pseudunio flabellatus (Goldfuss, 1837) †
- Species Unio wheatleyanus I. Lea, 1856 accepted as Diplodon (Rhipidodonta) burroughianus (I. Lea, 1834)
- Species Unio wheatleyi I. Lea, 1857 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio whitecliffsensis R. B. Newton, 1915 † accepted as Hyridella whitecliffsensis (R. B. Newton, 1915) †
- Species Unio whitei J. Henderson, 1918 † accepted as Ligumia whitei (J. Henderson, 1918) †
- Species Unio whiteianus I. Lea, 1852 accepted as Elliptio icterina (Conrad, 1834)
- Species Unio wianamattensis Etheridge, 1888 † accepted as Unionella wianamattensis (Etheridge, 1888) †
- Species Unio wilbrahamensis (B. K. Emerson, 1900) †
- Species Unio wilhelmi Penecke, 1883 † accepted as Potomida wilhelmi (Penecke, 1883) †
- Species Unio willcocksi R. B. Newton, 1899 † accepted as Unio abyssinicus E. von Martens, 1866
- Species Unio willistoni Logan, 1900 †
- Species Unio wilsonii I. Lea, 1859 accepted as Velesunio wilsonii (I. Lea, 1859)
- Species Unio wochtschabertica Radopulo, 1949 †
- Species Unio wolffi Modell, 1931 †
- Species Unio wolwichii Morelet, 1845
- Species Unio woodwardianus "I. Lea, 1859" accepted as Unio woodwardius I. Lea, 1857
- Species Unio woodwardius I. Lea, 1857 accepted as Ptychobranchus foremanianus (I. Lea, 1842)
- Species Unio wrightii I. Lea, 1865 accepted as Nodularia douglasiae (J. E. Gray, 1833)
- Species Unio wuerheensis J.-M. Wei, 1984 †
- Species Unio wymanii I. Lea, 1860 accepted as Diplodon wymanii (I. Lea, 1860)
- Species Unio wynegungaensis I. Lea, 1860 accepted as Parreysia corrugata (O. F. Müller, 1774)
- Species Unio xibeiensis B.-Y. Huang & J.-M. Wei, 1976 †
- Species Unio xietanensis J.-S. Yu, 1987 †
- Species Unio xuefengchuanensis B.-P. Liu & Z.-S. Li, 1980 †
- Species Unio yadkinensis I. Lea, 1872 accepted as Elliptio complanata ([Lightfoot], 1786)
- Species Unio yanbianensis Z.-W. Gu, 1976 †
- Species Unio yangcaogouensis J.-S. Yu & G.-Y. Dong, 1993 †
- Species Unio yirijinxiensis X.-Z. Liu, 1988 †
- Species Unio yueshanensis B.-L. Ding & J.-H. Li, 1982 †
- Species Unio yunnanensis Q.-H. Ma, 1976 † accepted as Qiyangia yunnanensis (Q.-H. Ma, 1976) †
- Species Unio yzabalensis Crosse & P. Fischer, 1893 accepted as Nephronaias yzabalensis (Crosse & P. Fischer, 1893)
- Species Unio zabulonicus Locard, 1883 accepted as Unio terminalis Bourguignat, 1852
- Species Unio zairglauensis [sic] † accepted as Unio zhairtauensis J.-M. Wei, 1984 †
- Species Unio zambesiensis Preston, 1905 accepted as Coelatura kunenensis (Mousson, 1888)
- Species Unio zeiglerianus I. Lea, 1838 accepted as Leaunio vanuxemensis (I. Lea, 1838)
- Species Unio zelebori Dunker, 1866 accepted as Unio caffer Krauss, 1848
- Species Unio zelebori M. Hörnes, 1864 † accepted as Potomida zelebori (M. Hörnes, 1864) †
- Species Unio zematicus Issel, 1885
- Species Unio zhairtauensis J.-M. Wei, 1984 †
- Species Unio zhaozhouensis Z.-W. Gu, 1999 †
- Species Unio zhengziensis X.-Z. Liu, 1984 †
- Species Unio zhenlaiensis Z.-W. Gu, 1999 †
- Species Unio zhungarica J.-M. Wei, 1984 † accepted as Unio zhungaricus J.-M. Wei, 1984 †
- Species Unio zhungaricus J.-M. Wei, 1984 †
- Species Unio zhuzhouensis Z.-R. Zhou, 1977 †
- Species Unio zigzag I. Lea, 1829 accepted as Truncilla donaciformis (I. Lea, 1827)
- Species Unio zitteli Penecke, 1883 † accepted as Cuneopsidea zitteli (Penecke, 1883) †
- Species Unio zonatus Heude, 1883 accepted as Aculamprotula zonata (Heude, 1883)
- Species Unio zsigmondyi Halaváts, 1888 † accepted as Potomida wilhelmi (Penecke, 1883) †
- Species Unio zujovici Pavlović, 1931 †
- Species Unio zvonimiri Brusina, 1902 †
- Genus Unionea Rafinesque, 1815 accepted as Unio Philipsson, 1788
- Genus Uniopsis Swainson, 1840 accepted as Alasmidonta Say, 1818
- Genus Utterbachia F. C. Baker, 1927 accepted as Utterbackia F. C. Baker, 1927
- Genus Strophitinae M. E. Gordon, 1981 accepted as Strophitinae Starobogatov, 1970
- Family Deccanoidea N. H. Shah & Patel, 2024 † accepted as Deccanoidoidea N. H. Shah & Patel, 2024 †
- Family Pachycardiidae L. R. Cox, 1961 † accepted as Trigonodidae Modell, 1942 †
- Family Silesunionina Skawina & Dzik, 2011 † accepted as Silesunionoidea Skawina & Dzik, 2011 †
- Genus Araripenaia V. R. Silva et al., 2020 † (1)
- Family Lyrodesmatidae P. Fischer, 1886 † (8)
- Family Pseudarcidae Scarlato & Starobogatov, 1979 † (3)
- Family Thoraliidae N. J. Morris, 1980 †
- Superorder Heteroconchia incertae sedis † (1)
- Infraclass Pteriomorphia (6 644)
- Subclass Bivalvia incertae sedis (7)
- Subclass Palaeotaxodonta accepted as Nuculida
- Subclass Paleoheterodonta accepted as Palaeoheterodonta
- Subclass Protobranchia (1 365)
- Infraclass Cryptodonta † (342)
- Class Caudofoveata (143)
- Class Cephalopoda (1 832)
- Class Conchifera accepted as Bivalvia
- Class Cricoconarida † (1)
- Class Gastropoda (102 679)
- Class Lamellibranchiata accepted as Bivalvia
- Class Loricata accepted as Polyplacophora
- Class Mollusca incertae sedis † (372)
- Class Monoplacophora (229)
- Class Pelecypoda accepted as Bivalvia
- Class Polyplacophora (1 377)
- Class Polyplaxiphora accepted as Polyplacophora
- Class Rostroconchia † (64)
- Class Scaphopoda (752)
- Class Solenoconchia accepted as Scaphopoda
- Class Solenogastres (313)
- Subclass Chaetodermomorpha accepted as Caudofoveata
