Cassowaries (Indonesian: kasuari; Biak: man suar 'bird strong'; Tok Pisin: muruk; Papuan: kasu weri 'horned head') are flightless birds of the genus Casuarius, in the order Casuariiformes. They are classified as ratites, flightless birds without a keel on their sternum bones. Cassowaries are native to the tropical forests of New Guinea (Western New Guinea and Papua New Guinea), the Moluccas (Seram and Aru Islands), and northeastern Australia.
Three cassowary species are extant. The most common, the southern cassowary, is the third-tallest and second-heaviest living bird, smaller only than the ostrich and emu. The other two species are the northern cassowary and the dwarf cassowary; the northern cassowary is the most recently discovered and the most threatened. A fourth, extinct, species is the pygmy cassowary.