Australia

Australia, officially known as the Commonwealth of Australia, was the largest country in Oceania before the Great War.

Fallout

 * The skeleton of a horned kangaroo, a mutated creature native to Australia, can be found.

Fallout 2

 * Ymir is of Australian descent.
 * Another horned kangaroo skeleton can be found.

Wild Appalachia

 * The Australian termite beetle is mentioned in the Pioneer Scout entomology exam.
 * The Australian continent is mentioned in the Pioneer Scout mammologist exam.

Appearances
Australia is mentioned in Fallout, Fallout 2 and the Fallout 76 add-on Wild Appalachia.

Behind the scenes
Australia is a real world county of the same name, officially named the Commonwealth of Australia, a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands.