The Feathertail Glider (Acrobates pygmaeus) is the world's smallest gliding mammal. Although only the size of a very small mouse (65 to 80 mm and 10 to 14 g), it can leap and glide long distances from tree to tree, up to 25 metres. Like other gliding mammals, the Feathertail Glider has a skin membrane between the fore and hind legs; thicker than that of the other marsupials like the Sugar Glider, but smaller in proportion, extending only between the elbows and knees.

The most obvious feature of the Feathertail Glider, however, is the tail that gives it its name: it is about the same length as the combined head/body, quite thin, moderately prehensile, and almost hairless except for the two very obvious rows of long, stiff hairs on either side. The tail, when held straight, looks rather like a double-sided comb. It is used to grip twigs and small branches, and to control gliding flight: steering and then braking.

The coat is a uniform mid-grey, with dark patches around the eyes and often a white patch behind the ears. The underside is lighter; the ears are moderately large and rounded.