A possum (plural form: possums) is any of about 70 small to medium-sized arboreal marsupial species native to Australia, New Guinea, and Sulawesi (and introduced to New Zealand and China).
Possums are quadrupedal diprotodont marsupials with long thick tails. The smallest possum, indeed the smallest diprotodont marsupial, is the Tasmanian pygmy possum, with an adult head-body length of 70 mm (2 3/4 in.) and a weight of 10 g (3/8 oz.). The largest is the bear cuscus that may exceed 7 kg (15lb. 6oz.). Possums are typically nocturnal and at least partially arboreal. The various species inhabit most vegetated habitats, and several species have adjusted well to urban settings. Diets range from generalist herbivores or omnivores (the common brushtail possum) to specialist browsers of eucalyptus (greater glider), insectivores (mountain pygmy possum) and nectar-feeders (honey possum).