The quokka (/ˈkwɒkə/) (Setonix brachyurus), 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 kangaroos and wallabies), the quokka is herbivorous and mainly nocturnal.

Quokkas are found on some smaller islands off the coast of Western Australia, particularly Rottnest Island, just off Perth, and also Bald Island near Albany, and in isolated, scattered populations in forest and coastal heath between Perth and Albany. A small colony exists at the eastern limit of their range in a protected area of Two Peoples Bay Nature Reserve, where they co-exist with the critically endangered Gilbert's potoroo.

A quokka weighs 2.5 to 5.0 kg (5.5 to 11.0 lb) and is 40 to 54 cm (16 to 21 in) long with a 25-to-30 cm-long (9.8-to-11.8 in) tail, which is quite short for a macropod. It has a stocky build, well developed hind legs, rounded ears, and a short, broad head. Its musculoskeletal system was originally adapted for terrestrial bipedal saltation, but over its evolution, its system has been built for arboreal locomotion. Although looking rather like a very small kangaroo, it can climb small trees and shrubs up to 1.5 metres (4 ft 11 in). Its coarse fur is a grizzled brown colour, fading to buff underneath. The quokka is known to live for an average of 10 years.

Quokkas have a promiscuous mating system. After a month of gestation, females give birth to a single baby called a joey. Females can give birth twice a year and produce about 17 joeys during their lifespan. The joey lives in its mother's pouch for six months. Once it leaves the pouch, the joey relies on its mother for milk for two more months and is fully weaned around 8 months after birth. Females sexually mature after roughly 18 months. When a female quokka with a joey in her pouch is pursued by a predator, she may drop her baby onto the ground; the joey produces noises, which may serve to attract the predator's attention, while the mother escapes.

Quokkas have little fear of humans and commonly approach people closely, particularly on Rottnest Island, where a prevalent population exists. Though quokkas have a reputation of being the happiest animal on Earth, annually, a few dozen cases of quokkas biting people, especially children, are reported. There are certain restrictions regarding feeding. It is illegal for members of the public to handle the animals in any way, and feeding, particularly of "human food", is especially discouraged, as they can easily get sick. An infringement notice carrying a $300 fine can be issued by the Rottnest Island Authority for such an offence. The maximum penalty for animal cruelty is a $50,000 fine and a five-year prison sentence.

Quokkas can also be observed at several zoos and wildlife parks around Australia, including Perth Zoo, Taronga Zoo, Wild Life Sydney, and Adelaide Zoo. Physical interaction is generally not permitted without explicit permission from supervising staff.

Quokka behavior in response to human interaction has been examined in zoo environments. One brief study indicated fewer animals remained visible from the visitor paths when the enclosure was an open or walk-through environment. This may have been due to the quokkas acquiring avoidance behavior of visitors, which the authors propose has implications for stress management in their exhibition to the public.