The quokka, the only member of the genus Setonix, is a small macropod about the size of a domestic cat. Like other marsupials in the macropod family (such as the kangaroos and wallabies), the quokka is herbivorous and mainly nocturnal. It can be found on some smaller islands off the coast of Western Australia, in particular on Rottnest Island just off Perth and Bald Island near Albany. A small mainland colony exists in the protected area of Two Peoples Bay Nature Reserve, where they co-exist with Gilbert's potoroo.

The quokka was one of the first Australian mammals seen by Europeans. The Dutch mariner Samuel Volckertzoon wrote of sighting "a wild cat" on Rottnest Island in 1658. In 1696, Willem de Vlamingh mistook them for giant rats and named the island "Rotte nest", which comes from the Dutch words rattennest meaning "rat nest". The word quokka is derived from a Nyungar word, which was probably gwaga.

The quokka weighs 2.5 to 5 kilograms (5.5 to 11 lb) and is 40 to 90 centimetres (16 to 35 in) long with a 25 to 30 centimetres (9.8 to 12 in)-long tail, which is fairly short for a macropod. It has a stocky build, rounded ears, and a short, broad head. Although looking rather like a very small, dumpy kangaroo, it can climb small trees and shrubs. Its coarse fur is a grizzled brown colour, fading to buff underneath.

The quokka has no fear of humans and it is common for it to approach them closely, particularly on Rottnest Island. It is, however, illegal for members of the public on Rottnest Island to handle the animals in any way. An infringement notice carrying a A$300 fine can be issued by the Rottnest Island Authority for such behaviour. In addition, prosecution of the offense can result in a fine of up to $2,000.

In the wild, its roaming is restricted to a very small range in the South-West of Western Australia, with a number of small scattered populations on the mainland, one large population on Rottnest Island and a smaller population on Bald Island near Albany. The islands are free of foxes and cats. On Rottnest, quokkas are common and occupy a variety of habitats ranging from semi-arid scrub to cultivated gardens.

Although numerous on the small offshore islands, it has a very restricted range and is classified as vulnerable. On the mainland, where it is threatened by most introduced predatory species such as foxes, it requires dense ground cover for refuge. Clearfell logging and agricultural development has reduced this habitat, thus contributing to the decline of the species. The introduction of cats and dogs, as well as dingoes, has added to the problem, as has the clearing and burning of the remaining (swamp) lands.