Porphyrio is the swamphen or swamp hen bird genus in the rail family. It includes some smaller species of gallinules which are sometimes separated as genus Porphyrula or united with the gallinules proper in Gallinula. The Porphyrio gallinules are distributed in the warmer regions of the world. The group probably originated in Africa in the Middle Miocene, before spreading across the world in waves from the Late Miocene to Pleistocene.

Rails are a large, cosmopolitan family of small- to medium-sized terrestrial and/or semi-amphibious birds. The family exhibits considerable diversity in its forms, and includes such ubiquitous species as the crakes, coots, and gallinule; other rail species are extremely rare or endangered. Many are associated with wetland habitats, some being semi-aquatic like waterfowl, but many more are wading birds or shorebirds. The ideal rail habitats are marsh areas, including rice paddies, and flooded fields or open forest. They are especially fond of dense vegetation for nesting. The rail family is found in every terrestrial habitat with the exception of dry desert, polar or freezing regions, and alpine areas. Members of Rallidae occur on every continent except Antarctica. Numerous unique island species are known.