Moorhens, sometimes called marsh hens, are medium-sized water birds that are members of the rail family Rallidae. They constitute the genus Gallinula. They are close relatives of coots, and because of their apparently nervous behavior (frequently twitching tail, neck and grinding their backs) are sometimes called "skitty coots". Often, they are referred to as (black) gallinules.

A few species from the Australian region, sometimes separated in Tribonyx, are called native-hens. Tribonyx is better considered a subgenus however as the differences are not very striking and mainly plesiomorphic. 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.

These rails are mostly brown and black with some white markings in plumage colour. Unlike many of the rails they are usually easy to see, feeding in open water margins rather than hidden in reedbeds.

They have short rounded wings and are weak fliers, although usually capable of covering long distances. The Common Moorhen in particular migrates up to 2,000 km from some of its breeding areas in the colder parts of Siberia. Those that migrate do so at night. The Gough Island Moorhen on the other hand is considered almost flightless—it can only flutter some metres. As common in rails, there has been a marked tedency to evolve flightlessness in island populations.

Moorhens can walk very well on strong legs, and have long toes that are well adapted to soft uneven surfaces.

These birds are omnivorous taking plant material, small rodents, amphibians and eggs. They are aggressively territorial during the breeding season, but are otherwise often found in sizeable flocks on the shallow vegetated lakes they prefer.