• Acanthocheilonema spirocauda (Leidy, 1858)
• Acanthocheilus rotundatus (Rudolphi, 1819)
• Acantholaimus elegans Jensen, 1988
• Acantholaimus ewensis Platt & Zhang, 1982 accepted as Acantholaimus polydentatus Gerlach, 1951
• Acantholaimus iubilus Gerlach, Schrage & Riemann, 1979
• Acantholaimus longisetosus Allgén, 1933
• Acantholaimus megamphis Vivier, 1985
• Acantholaimus minima (Vitiello, 1970) Gerlach, Schrage & Riemann, 1979 accepted as Acantholaimus minutus (Vitiello, 1972) Gerlach, Schrage & Riemann, 1979
• Acantholaimus minutus (Vitiello, 1972) Gerlach, Schrage & Riemann, 1979
• Acantholaimus polydentatus Gerlach, 1951
• Acantholaimus setosus Vitiello, 1970
• Acantholaimus spinicauda (Vitiello, 1970) Gerlach, Schrage & Riemann, 1979
• Acanthonchus (Acanthonchus) arcuatus (Kreis, 1928) Wieser, 1955
• Acanthonchus (Acanthonchus) viviparus Cobb, 1920
• Acanthonchus (Seuratiella) gracilis (Ditlevsen, 1918) Wieser, 1955
• Acanthonchus (Seuratiella) pugionatus Vitiello, 1970
• Acanthonchus viviparus Cobb, 1920 accepted as Acanthonchus (Acanthonchus) viviparus Cobb, 1920
• Acanthopharyngoides tyrrhenicus Wieser, 1954
• Acanthopharynx affinis Marion, 1870
• Acanthopharynx micans (Eberth, 1863) Marion, 1870
• Acanthopharynx micramphis Schuurmans Stekhoven, 1942
• Acanthopharynx perarmata Marion, 1870
• Acanthopharynx rigida Schuurmans Stekhoven, 1950
• Acanthopharynx setosissima Schuurmans Stekhoven, 1943 (uncertain > taxon inquirendum)
• Achromadora buikensis (Steiner, 1921) Mikoletzky, 1925 accepted as Achromadora micoletzkyi (Stefanski, 1915) Van der Linde, 1938
• Achromadora dubia sensu Micoletzky, 1925 accepted as Achromadora inermis Altherr, 1952
• Achromadora inermis Altherr, 1952
• Achromadora micoletzkyi (Stefanski, 1915) Micoletzky, 1925
• Achromadora micoletzkyi (Stefanski, 1915) Van der Linde, 1938
• Achromadora ruricola (De Man, 1880) Micoletzky, 1924
• Achromadora terricola (de Man, 1880) Micoletzky, 1924
• Acontiolaimus zostericola Filipjev, 1918 (uncertain > taxon inquirendum)
• Actarjania pomarei Boucher, 1973 accepted as Sabatieria pomarei (Boucher, 1973)
• Actinonema celtica Boucher, 1976
• Actinonema fidatum Vitiello, 1970
• Actinonema longicaudatum (Steiner, 1918) Wieser, 1954
• Actinonema pachydermatum Cobb, 1920
• Adeuchromadora megamphida Boucher & Bovée, 1972 accepted as Actinonema pachydermatum Cobb, 1920
• Adoncholaimus derjugini (Ssaweljev, 1912)
• Adoncholaimus fuscus (Bastian, 1865) Filipjev, 1918
• Adoncholaimus islandicus Kreis, 1963
• Adoncholaimus lepidus (de Man, 1889) Filipjev, 1918
• Adoncholaimus panicus Cobb, 1930
• Adoncholaimus thalassophygas (de Man, 1876) Filipjev, 1918
• Aegialoalaimus elegans de Man, 1907
• Aegialoalaimus punctatus (Allgén, 1929) (uncertain > taxon inquirendum)
• Aegialoalaimus sabulicola Allgén, 1933 (uncertain > taxon inquirendum)
• Aegialoalaimus tenuicaudatus Allgén, 1932 (uncertain > taxon inquirendum)
• Aegialoalaimus tenuis Kreis, 1928 (uncertain > taxon inquirendum)
• Agamascaris septentrionalis Kreis, 1952 (uncertain > nomen dubium)
• Aglenchus agricola (de Man, 1884) Andrássy, 1954
• Alaimella cincta Cobb, 1920
• Alaimus acutus Thorne, 1939
• Alaimus editorus Siddiqi & Husain, 1967
• Alaimus hamulus Siddiqi & Husain, 1967
• Alaimus meyli Andrássy, 1961
• Alaimus parvus Thorne, 1939
• Alaimus primitivus de Man, 1880
• Allgeniella pachydema (G.Schneider, 1926) Allgén, 1947 accepted as Chromadorita pachydema (G. Schneider, 1926) Wieser, 1954
• Allodiplogaster pararmata (W. Schneider, 1938) Kanzaki, Ragsdale & Giblin-Davis, 2014
• Amidostomum acutum (Lundahl, 1848)
• Ammotheristus helgolandicus (Riemann, 1967) Lorenzen, 1977
• Ammotheristus subtilis (Lorenzen, 1972) Lorenzen, 1977
• Amphidelus puccinelliae Lorenzen, 1966 accepted as Paramphidelus puccinelliae (Lorenzen, 1966)
• Amphidelus stefanskii Juget, 1969
• Amphimonhystera anechma (Southern, 1914) Lorenzen, 1977
• Amphimonhystera helgolandica Riemann, 1967 accepted as Ammotheristus helgolandicus (Riemann, 1967) Lorenzen, 1977
• Amphimonhystera paranechma Allgén, 1935 (uncertain > taxon inquirendum)
• Amphimonhystera subtilis Lorenzen, 1972 accepted as Ammotheristus subtilis (Lorenzen, 1972) Lorenzen, 1977
• Anaplectus granulosus (Bastian, 1865) De Coninck & Schuurmans Stekhoven, 1933
• Anguillicola (Anguillicoloides) crassus Kuwahara, Niimi & Itagaki, 1974 accepted as Anguillicola crassus Kuwahara, Niimi & Itagaki, 1974
• Anguillicola crassus Kuwahara, Niimi & Itagaki, 1974
• Anguillicoloides crassus (Kuwahara, Niimi & Itagaki, 1974) Moravec & Taraschewski, 1988 accepted as Anguillicola crassus Kuwahara, Niimi & Itagaki, 1974
• Anguinoides profundus (Vitiello, 1974) Holovachov, 2003 accepted as Procamacolaimus profundus Vitiello, 1974
• Anisakis berlandi Mattiucci, Cipriani, Webb, Paoletti, Marcer, Bellisario, Gibson & Nascetti, 2014
• Anisakis pegreffii Campana-Rouget & Biocca, 1955
• Anisakis physeteris Baylis, 1923 accepted as Skrjabinisakis physeteris (Baylis, 1923) Safonova, Voronova & Vainutis, 2021
• Anisakis schupakovi Mosgovoi, 1951 accepted as Skrjabinisakis schupakovi Mozgovoy, 1951
• Anisakis simplex (Rudolphi, 1809) Dujardin, 1845
• Anisakis simplex_C of Nascetti, Paggi, Orecchia, Smith, Mattiucci & Bullini, 1986 accepted as Anisakis berlandi Mattiucci, Cipriani, Webb, Paoletti, Marcer, Bellisario, Gibson & Nascetti, 2014
• Anisakis typica (Diesing, 1860) Baylis, 1920
• Anisakis ziphidarum Paggi, Nascetti, Webb, Mattiucci, Cianchi & Bullini, 1988
• Anomonema deconincki Jensen, 1976
• Anoplostoma blanchardi de Man, 1888 accepted as Anoplostoma campbelli Allgén, 1932
• Anoplostoma campbelli Allgén, 1932
• Anoplostoma elegans Kreis, 1929
• Anoplostoma exceptum Schulz, 1935
• Anoplostoma viviparum (Bastian, 1865) Bütschli, 1874
• Anticoma acuminata (Eberth, 1863) Bastian, 1865
• Anticoma arctica Steiner, 1916
• Anticoma brevicaudata Kreis, 1963
• Anticoma brevisetosa Platonova, 1967
• Anticoma eberthi Bastian, 1865
• Anticoma ecotronis Boucher, 1977
• Anticoma insulaealbae Filipjev, 1927
• Anticoma limalis Bastian, 1865 accepted as Anticoma acuminata (Eberth, 1863) Bastian, 1865
• Anticoma limalis novozemelica Filipjev, 1927 accepted as Anticoma acuminata (Eberth, 1863) Bastian, 1865
• Anticoma longicaudata Kreis, 1928
• Anticoma minor Filipjev, 1927
• Anticoma murmanica Filipjev, 1927 accepted as Odontanticoma murmanica (Filipjev, 1927) Platonova, 1976