Hydrozoa Owen, 1843
Acaulidae Fraser, 1924
Asyncorinidae
Asyncorynidae Kramp, 1949
Australomedusidae Russell, 1971
Axoporidae Boschma, 1951
Balellidae Stechow, 1922
Boeromedusidae Bouillon, 1995
Boreohydridae Westblad, 1947
Bougainvilliidae Lütken, 1850
Brinckmannia Schuchert & Reiswig, 2006
Bythotiaridae Maas, 1905
Candelabridae Stechow, 1921
Cladocorynidae Allman, 1872
Cladonematidae Gegenbaur, 1857
Cladosarsiidae
Clathrozoellidae Peña Cantero, Vervoort & Watson, 2003
Cordylophoridae von Lendenfeld, 1885
Corymorphidae Allman, 1872
Corynidae Johnston, 1836
Cytaeididae L. Agassiz, 1862
Eucodoniidae Schuchert, 1996
Eudendriidae L. Agassiz, 1862
Halimedusidae Arai & Brinckmann-Voss, 1980
Heterastridiidae
Heterotentaculidae Schuchert, 2010
Hydractiniidae L. Agassiz, 1862
Hydrichthyidae
Hydridae Dana, 1846
Hydrocorynidae Rees, 1957
Jeanbouilloniidae Pagès, Flood & Youngbluth, 2006
Magapiidae Schuchert & Bouillon, 2009
Margelopsidae Uchida, 1927
Microcampana Fewkes, 1889
Milleporidae Fleming, 1828
Moerisiidae Poche, 1914
Niobiidae Petersen, 1979
Oceaniidae Eschscholtz, 1829
Pachycordylidae
Pandeidae Haeckel, 1879
Paracorynidae
Paulinum Brinckmann-Voss & Arai, 1998
Pennariidae McCrady, 1859
Polyorchidae Agassiz, 1862
Porpitidae Goldfuss, 1818
Proboscidactylidae Hand & Hendrickson, 1950
Propachycordyle Thiel, 1931
Protiaridae Haeckel, 1879
Protohydridae
Pseudodiscophyllum Fryer & Stanley, 2004
Pseudosolanderiidae
Ptilocodiidae Coward, 1909
Rathkeidae Russell, 1953
Rhysiidae (Hickson & Gravely, 1907)
Rosalindidae Bouillon, 1985
Saccohydra Billard, 1914
Solanderiidae Marshall, 1892
Sphaerocorynidae Prévot, 1959
Stylasteridae Gray, 1847
Teissieridae Bouillon, 1978
Tetraralphia Pagès & Bouillon, 1997
Trichydridae Hincks, 1868
Tricyclusidae Kramp, 1949
Tubiclavoididae Moura, Cunha & Schuchert, 2007
Tubidendridae Nutting, 1905
Tubulariidae Fleming, 1828
Turbulariidae
Zancleidae Russell, 1953
Zancleopsidae Bouillon, 1978