About the same size as a cat, the common ringtail possum is gray, with orange-brown tinges on its legs and tail, and white patches on its belly and behind the eyes, and a white tip to its tail. It uses its long prehensile tail as a fifth limb to enable it to climb and jump from branch to branch and between fences and powerlines. The gap between its second and third fingers on its forefeet means that it can hold onto branches securely.
Common ringtail possums are to be found along Australia’s eastern coastline, Western Australia’s southwestern corner and in Tasmania. They live in tropical or temperate areas, rarely in drier areas, usually in dense brush forests which are plentiful with eucalyptus.
Ringtail possums are territorial, marking their territory with scented secretions. The common ringtail possum is not solitary, unlike many other species of ringtail possum, and usually forms small groups, typically of one adult male with one to two adult females and their offspring from the last breeding season. Such family groups live in nests which they build, called dreys. These possums are nocturnal, so are most active during the night. They are well adapted to living in trees and are not often found on the ground. Common ringtail possums communicate by means of vocalizations.
Common ringtail possums, being monogamous, remain with one partner only. Both male and female build their drey together and will readily move to another one, along with their young. Breeding occurs from April to December. Males and females are both sexually mature by the mating season following their birth. Gestation lasts about 4 months and they usually have one or two litters each year, usually 2 babies, although 1 to 4 have been recorded. The newborn babies crawl into their mother’s pouch and stay attached to a nipple from 42 to 49 days, remaining in the pouch for another 4 months or so. Once they leave the pouch, they cling to their mother's back or stay in the nest until weaning occurs at about 6 months. Both parents often care for the young, the father carrying them around while the mother feeds.
These animals have suffered loss of habitat from deforestation, due to the fact that they are almost exclusively arboreal. In built-up areas they are in danger of being struck by cars, and hunted by cats and dogs.
The common ringtail possum numbers have not been calculated, but populations seem to be stable and they are not threatened.