a genus of marsupial mammals of the family Phalangeridae. There is a single species, the koala (P. cinereus). The body is 60–82 cm long and weighs up to 16 kg; the extremely short tail is barely visible. Koalas resemble bears in appearance. The gray fur is thick and soft, and the pouch is well developed and opens in the rear. The first and second fingers and the first toes are opposable to the other digits; the digits evolved in this fashion as an adaptation to arboreal life.

Koalas are found in the eucalyptus forests of eastern Australia, where they dwell in treetops. They are nocturnal animals and appear singly or in small groups. Adult males usually have a harem. The diet consists of eucalyptus leaves. The breeding season is from September to May, and the gestation period is 30 days. The single young remains in the pouch for about six months.

Greatly reduced in number in the past by slaughter for their fur, koalas are now fully protected and have increased in number. Some zoologists classify the koala in a separate family.