Trematoda Rudolphi, 1808
Allassogonoporidae Odening, 1964
Allocreadiidae Looss, 1902
Anchitrematidae Mehra, 1935
Anenterotrematidae Yamaguti, 1958
Angiodictyidae
Apocreadiidae Skrjabin, 1942
Atractotrematidae Yamaguti, 1939
Auridistomatidae
Auridistomidae Stunkard, 1924
Balanorchiidae Stunkard, 1925
Bathcotylidae
Batrachotrematidae Dollfus & Williams, 1966
Brachycladiidae Odhner, 1905
Brachycoelidae
Brachycoeliidae Odening, 1964
Braunotrematidae Yamaguti, 1958
Brumptiidae Stunkard, 1925
Bunocotylidae
Callodistomatidae
Callodistomidae Odhner, 1910
Calycodidae Dollfus, 1929
Cephalogonimidae Looss, 1899
Cephaloporidae
Choanocotylidae Jue Sue & Platt, 1998
Choerocotylidae Yamaguti, 1971
Collyriclidae Ward, 1917
Cortrematidae Yamaguti, 1958
Derogenidae Nicoll, 1910
Deropristidae Cable & Hunninen, 1942
Deropristiidae Skrjabin, 1958
Dicrocoeliidae Looss, 1899
Diplangidae Yamaguti, 1971
Dolichoperidae
Dolichoperoididae Johnston & Angel, 1940
Echinoporidae Krasnolobova & Timofeeva, 1965
Encotylidae
Encyclometridae Mehra, 1931
Enenteridae Yamaguti, 1958
Eucotylidae Skrjabin, 1924
Eumegacetidae Travassos, 1922
Eurotrematidae
Exotidendriidae Mehra, 1935
Faustulidae Poche, 1926
Fellodistomidae Nicoll, 1909
Gekkonotrematidae Yamaguti, 1971
Glypthelminthidae Cheng, 1959
Gorgocephalidae Manter, 1966
Gorgoderidae Looss, 1899
Gyliauchenidae Fukui, 1929
Gyrabascidae Macy, 1935
Haematoloechidae Odening, 1964
Haplometridae
Homalometridae Mehra, 1962
Labicolidae Blair, 1979
Laterotrematidae Yamaguti, 1958
Lecithodendriidae Lühe, 1901
Lepocreadiidae Odhner, 1905
Leptophallidae Dayal, 1938
Leyogonimidae Dollfus, 1951
Liliatrematidae Gubanov, 1953
Lissorchiidae Magath, 1917
Macroderidae
Macroderoididae McMullen, 1937
Maseniidae
Meristocotylidae Fischthal & Kuntz, 1981
Mesocoeliidae Dollfus, 1933
Mesotretidae Poche, 1926
Microphallidae Ward, 1901
Monorchiidae Odhner, 1911
Nanophyetidae Dollfus, 1939
Nuitrematidae Kurochkin, 1975
Ocadiatrematidae Fischthal & Kuntz, 1981
Ochetosomatidae
Octotestidae
Olveriidae Yamaguti, 1958
Omphalometridae Looss, 1899
Opecoelidae Ozaki, 1925
Opisthogonimidae Travassos, 1928
Opistholebetidae Fukui, 1929
Orientocreadiidae Yamaguti, 1958
Pachypsolidae Yamaguti, 1958
Paragonimidae Dollfus, 1939
Paramphistomidae Fischoeder, 1901
Phaneropsolidae Mehra, 1935
Plagiorchiidae Lühe, 1901
Pleorchiidae Poche, 1926
Pleurogenidae Looss, 1899
Prosthogonimidae Nicoll, 1924
Prouterinidae Foreyt, Schell & Beyer, 1996
Psilostomidae Looss, 1900
Renicolidae Dollfus, 1939
Reniferidae Pratt, 1902
Renschetrematidae Yamaguti, 1971
Rhytidodidae Odhner, 1926
Sclerodistomoididae Gibson & Bray, 1979
Steganodermatidae Dollfus, 1952
Stomylotrematidae Poche, 1926
Styphlotrematidae Baer, 1924
Taiwantrematidae Fischthal & Kuntz, 1981
Tandanicolidae Johnston, 1927
Telorchiidae Nicoll, 1924
Thrinascotrematidae Jue Sue & Platt, 1999
Troglotrematidae Odhner, 1914
Zonocotylidae Yamaguti, 1963
Zoogonidae Odhner, 1902
Zygocotylidae Ward, 1917