Hydractinia is een geslacht van neteldieren uit de  familie van de Hydractiniidae.

Soorten 
 Hydractinia aculeata (Wagner, 1833)
 Hydractinia aggregata Fraser, 1911
 Hydractinia altispina Millard, 1955
 Hydractinia anechinata (Ritchie, 1907)
 Hydractinia angusta Hartlaub, 1904
 Hydractinia apicata (Kramp, 1959)
 Hydractinia arctica (Jäderholm, 1902)
 Hydractinia arge (Clarke, 1882)
 Hydractinia armata Fraser, 1940
 Hydractinia bayeri Hirohito, 1984
 Hydractinia betkensis (Watson, 1978)
 Hydractinia brachyurae (Hirohito, 1988)
 Hydractinia californica Torrey, 1904
 Hydractinia canalifera Millard, 1957
 Hydractinia carica Bergh, 1887
 Hydractinia carolinae Fraser, 1912
 Hydractinia cryptogonia Hirohito, 1988
 Hydractinia cytaeiformis Vervoort, 2006
 Hydractinia denhami (Thornely, 1904)
 Hydractinia diogenes Millard, 1959
 Hydractinia disjuncta Fraser, 1938
 Hydractinia dongshanensis Xu & Huang, 2006
 Hydractinia echinata (Fleming, 1828)
 Hydractinia epidocleensis Leloup, 1931
 Hydractinia epispongia Fraser, 1938
 Hydractinia gorgonoides (Nutting, 1906)
 Hydractinia granulata Hirohito, 1988
 Hydractinia guangxiensis Huang, Li & Zhang, 2010
 Hydractinia hancocki Fraser, 1938
 Hydractinia inabai (Hirohito, 1988)
 Hydractinia ingolfi Kramp, 1932
 Hydractinia kaffraria Millard, 1955
 Hydractinia laevispina Fraser, 1922
 Hydractinia longispina Fraser, 1938
 Hydractinia mar (Gasco & Calder, 1993)
 Hydractinia marsupialia Millard, 1975
 Hydractinia meteoris (Thiel, 1938)
 Hydractinia michaelseni Broch, 1914
 Hydractinia minoi (Alcock, 1892)
 Hydractinia moniliformis Huang, Zhong & Zhang, 2010
 Hydractinia monocarpa Allman, 1876
 Hydractinia monoon (Hirohito, 1988)
 Hydractinia multispina Fraser, 1938
 Hydractinia multitentaculata (Millard, 1975)
 Hydractinia munita (Calder, 2010)
 Hydractinia nagaoensis Bouillon, Medel & Peña Cantero, 1997
 Hydractinia novaezelandiae Schuchert, 1996
 Hydractinia ocalana (Brooks, 1964) †
 Hydractinia ocellata (Agassiz & Mayer, 1902)
 Hydractinia otagoensis (Schuchert, 1996)
 Hydractinia pacifica Hartlaub, 1905
 Hydractinia parvispina Hartlaub, 1905
 Hydractinia paucispinata Vervoort, 2006
 Hydractinia phialiformis (Antsulevich, 1983)
 Hydractinia piscicola (Komai, 1932)
 Hydractinia polycarpa Fraser, 1938
 Hydractinia polyclina L. Agassiz, 1862
 Hydractinia polytentaculata Xu & Huang, 2006
 Hydractinia proboscidea (Hincks, 1868)
 Hydractinia prolifica Fraser, 1948
 Hydractinia promiscua Galea & Ferry, 2015
 Hydractinia quadrigemina Fraser, 1938
 Hydractinia recurvatus Lin, Xu, Huang & Wang, 2010
 Hydractinia rugosa Fraser, 1938
 Hydractinia sarsii (Steenstrup, 1850)
 Hydractinia spinipapillaris (Hirohito, 1988)
 Hydractinia spiralis Goto, 1910
 Hydractinia symbiolongicarpus Buss & Yund, 1989
 Hydractinia symbiopollicaris Buss & Yund, 1989
 Hydractinia thatcheri Chapman, 1931 †
 Hydractinia uniformis Stampar, Tronolone & Morandini, 2006
 Hydractinia vacuolata Xu & Huang, 2006
 Hydractinia valens Fraser, 1943
 Hydractinia vallini Jäderholm, 1926
 Hydractinia verdi Ritchie, 1907
 Hydractinia yerii (Iwasa, 1934)

Hydractiniidae