A wallaby is any of about thirty species of macropod (Family Macropodidae). A wallaby is any macropod that isn’t large enough to be considered a kangaroo and has not been given some other name. There is no fixed dividing line. In general, a wallaby is smaller and has a stockier build than a kangaroo. A wallaroo is any of a few species somewhat intermediate in size between a wallaby and a kangaroo. Very small forest-dwelling wallabies are known as pademelons (genus Thylogale) and dorcopsises (genera Dorcopsis and Dorcopsulus). Young wallabies are known as “joeys”, like many other marsupials.

Wallabies are widely distributed across Australia, particularly in more remote, heavily timbered, or rugged areas. Not as much on the great semi-arid plains that are better suited to the larger, leaner, and more fleet-footed kangaroos. A small colony of introduced wallabies can also be found near Waimate in southern New Zealand.

Wallabies are not a distinct biological group. Nevertheless they fall into several broad categories. Typical wallabies of the Macropus genus, like the Agile Wallaby (Macropus agilis), and the Red-necked Wallaby (Macropus rufogriseus) are most closely related to the kangaroos and wallaroos. Other than size, they look very similar. These are the ones most frequently seen, particularly in the southern states.

Rock wallabies (genus Petrogale) specialize in rugged terrain. They have modified feet designed to grip rock with skin friction rather than dig into soil with large claws. There are at least fifteen species and the relationship between several of them is poorly understood. Several are endangered.

The Banded Hare-Wallaby (Lagostrophus fasciatus) is thought to be the last remaining member. Once common across southern Australia, it is now restricted to two islands off the Western Australian coast which are free of introduced predators. It is not as closely related to the other hare wallabies (genus Lagorchestes) as the hare wallabies are to the other wallabies.

New Guinea has at least five species of wallaby.

Additionally, a small wild population of wallabies is known to exist in Hawaii, in the upper regions of Kalihi Valley of the island of Oahu. This colony arose from an escape of zoo specimens.