• Alle Link, 1806
• Alle alle (Linnaeus, 1758)
• Allechinostomatinae Sudarikov, 1950 accepted as Echinochasminae Odhner, 1910 accepted as Echinochasmidae Odhner, 1910
• Allechinostomum Odhner, 1910 accepted as Echinochasmus Dietz, 1909
• Allechinostomum crocodili (Poirier, 1886) Odhner, 1910 accepted as Echinochasmus crocodili (Poirier, 1886)
• Allechinostomum famelicum Odhner, 1910 accepted as Echinochasmus famelicus (Odhner, 1910) Prudhoe, 1944
• Allechinostomum nigriciconiatum Ku, Chiu, Li & Chu, 1974 accepted as Echinochasmus nigriciconiatum (Ku, Chiu, Li & Chu, 1974)
• Allechinostomum renale Yeh, 1954 accepted as Ignavia renalis (Yeh, 1954) Wright, 1957
• Alleena Marcus, 1947 accepted as Latocestus Plehn, 1896
• Alleena callizona Marcus, 1947 accepted as Latocestus callizona (Marcus, 1947)
• Alleena mexicana Hyman, 1953 accepted as Latocestus mexicana (Hyman, 1953)
• Alleghenya Clench & Boss, 1967 accepted as Leptoxis Rafinesque, 1819
• Allelogromia De Saedeleer, 1934 accepted as Diplogromia Rhumbler, 1904
• Allelogromia brunnerii (Blanc, 1896) accepted as Diplogromia brunnerii (Blanc, 1886)
• Allemannites Grün (uncertain > nomen dubium)
• Allemannites romani (Górka) Górka
• Allenbatrachus Greenfield, 1997
• Allenbatrachus grunniens (Linnaeus, 1758)
• Allenbatrachus meridionalis Greenfield & Smith, 2004
• Allenbatrachus reticulatus (Steindachner, 1870)
• Allencotyla Price, 1962
• Allencotyla lutini El-Dien, 1995
• Allencotyla mcintoshi Price, 1962
• Allencotyla pricei Kritsky, Noble & Moser, 1978 accepted as Pseudoallencotyla pricei (Kritsky, Noble & Moser, 1978) Montero, Aznar, Fernández & Raga, 2003
• Allendea La Llave accepted as Liabum Adans.
• Allendea La Llave & Lex. accepted as Liabum Adans.
• Allendea lanceolata La Llave accepted as Liabum bourgeaui Hieron.
• Allenella Iredale, 1944
• Allenella belli Iredale, 1944
• Allenella belli extra Iredale, 1944 accepted as Allenella belli Iredale, 1944
• Allenella formalis Iredale, 1944
• Allenella formalis planorum Iredale, 1944 accepted as Allenella planorum Iredale, 1944
• Allenella planorum Iredale, 1944
• Allenichthys Pietsch, 1984
• Allenichthys glauerti (Whitley, 1944)
• Allenicordia Scarlato & Starobogatov, 1983 accepted as Lyonsiella G. O. Sars, 1872
• Allenina Fernández-Yépez, 1948 accepted as Curimata Bosc, 1817
• Allenina pectinata Fernández-Yépez, 1948 accepted as Steindachnerina leucisca (Günther, 1868)
• Allenina spiluropsis (Eigenmann & Eigenmann, 1889) accepted as Cyphocharax spiluropsis (Eigenmann & Eigenmann, 1889)
• Allenoconcha Preston, 1913
• Allenoconcha basispiralis Preston, 1913
• Allenoconcha belli Preston, 1913 accepted as Allenoconcha basispiralis Preston, 1913
• Allenoconcha congener Preston, 1913 accepted as Allenoconcha basispiralis Preston, 1913
• Allenoconcha mathewsi Preston, 1913 accepted as Allenoconcha basispiralis Preston, 1913
• Allenoconcha monspittensis Preston, 1913 accepted as Allenoconcha basispiralis Preston, 1913
• Allenoconcha perdepressa Preston, 1913 accepted as Allenoconcha basispiralis Preston, 1913
• Allenoconcha retinaculum (Preston, 1913)
• Allenoconcha royana Preston, 1913 accepted as Allenoconcha basispiralis Preston, 1913
• Allenocytheridea Ballent, 1980 †
• Allentula Iredale, 1958 accepted as Allenella Iredale, 1944
• Allentula belli (Iredale, 1944) accepted as Allenella belli Iredale, 1944
• Allentula formalis (Iredale, 1944) accepted as Allenella formalis Iredale, 1944
• Allentula planorum (Iredale, 1944) accepted as Allenella planorum Iredale, 1944
• Allentylenchus Khan & Saeed, 1988 accepted as Scutylenchus Jairajpuri, 1971
• Allentylenchus graminicola (Kirjanova, 1951) Khan & Saeed, 1988 accepted as Geocenamus graminicola (Kirjanova, 1951) Geraert, 2011
• Alleocarpa Michaelsen, 1900 accepted as Alloeocarpa Michaelsen, 1900
• Alleocarpa similis (Sluiter, 1904) accepted as Symplegma brakenhielmi (Michaelsen, 1904)
• Alleorus A. M. Strong, 1938 accepted as Discopsis de Folin, 1870
• Alleorus deprellus A. M. Strong, 1938 accepted as Discopsis deprellus (A. M. Strong, 1938)
• Allepithema Tomlin, 1931
• Allepithema concavospirum (Möllendorff, 1895)
• Allepithema euspirum (Möllendorff, 1895)
• Allepithema fulva (Quadras & Möllendorff, 1894) accepted as Allepithema fulvum (Quadras & Möllendorff, 1894)
• Allepithema fulvum (Quadras & Möllendorff, 1894)
• Allepithema glabrata (Quadras & Möllendorff, 1894) accepted as Allepithema glabratum (Quadras & Möllendorff, 1894)
• Allepithema glabratum (Quadras & Möllendorff, 1894)
• Allepithema meridionale (Möllendorff, 1888)
• Allepithema microconus (Quadras & Möllendorff, 1895)
• Allepithema nagayamai Kuroda, 1960
• Allepithema philippinense (Möllendorff, 1887)
• Allepithema pyramidatum (Möllendorff, 1893)
• Allepithema pyramis (Quadras & Möllendorff, 1894)
• Allepithema quadrasi (Möllendorff, 1894)
• Allepithema timorensis (B. Rensch, 1935)
• Allepithema tongkingense (Möllendorff, 1901)
• Allepithema tuberculata (Quadras & Möllendorff, 1894) accepted as Allepithema tuberculatum (Quadras & Möllendorff, 1894)
• Allepithema tuberculatum (Quadras & Möllendorff, 1894)
• Allepithema turrita (Quadras & Möllendorff, 1894) accepted as Allepithema turritum (Quadras & Möllendorff, 1894)
• Allepithema turritum (Quadras & Möllendorff, 1894)
• Allerescha Gordon, 1989
• Allerescha dubia Gordon, 1989
• Allertemmysa Schallreuter, 1974 †
• Allertemmysa prenaiensis (Neckaja, 1973) †
• Allerya Bourguignat, 1878 accepted as Gonyodiscus Fitzinger, 1833 accepted as Discus Fitzinger, 1833
• Allerya Mörch, 1877 accepted as Williamia Monterosato, 1884
• Allescheria R. Hartig, 1899
• Allescheria terrestris Apinis, 1963 accepted as Thielavia terrestris (Apinis) Malloch & Cain, 1972
• Allescheriella Henn., 1897
• Allescheriella bathygena Kohlm., 1977
• Alleurythoe Sun & Li, 2017
• Alleurythoe tenuichaeta Sun & Li, 2017
• Allexivirus
• Alleynea Womersley, 2003
• Alleynea bicornis Womersley, 2003