Moorhens—sometimes called marsh hens—are medium-sized water birds that are members of the rail family (Rallidae). Most species are placed in the genus Gallinula, Latin for "little hen". They are close relatives of coots. They are often referred to as (black) gallinules. Recently, one of the species of Gallinula was found to have enough differences to form a new genus Paragallinula with the only species being the lesser moorhen (Paragallinula angulata).

Two species from the Australian region, sometimes separated in Tribonyx, are called "native hens" (also native-hen or nativehen). The native hens differ visually by shorter, thicker and stubbier toes and bills, and longer tails that lack the white signal pattern of typical moorhens.