Australia was an island continent on Earth. Located in the southern hemisphere, it was the location of an eponymous nation-state. Inhabitants of Australia were known as Australians.
Australia was home to a prehistoric human culture, commonly called Aborigines. They had a complex philosophical system which included a concept called Dream-time. This culture was nearly wiped out in the 19th century, but had managed to survive into the 23rd century. (TOS novel: Strangers from the Sky)
In the late 18th century, a penal colony was established on Australia by the United Kingdom. English Captain Arthur Phillip attempted to establish a penal colony at Botany Bay on January 17, 1788. Poor soils and poor knowledge of the climate and country meant the colony was often facing starvation, but adjustment of farming techniques, discovery of richer lands ensured the prosperity of the colony. Other colonies were soon established. Gold rushes and an inclusive culture attracted millions of immigrants who forged a stable, inclusive and peaceful nation. In the 20th century, Khan Noonien Singh memorialized the colony by naming the sleeper ship his augment group had been provided with after the colony (TOS novel: The Rise and Fall of Khan Noonien Singh, Volume 2). (FASA RPG module: The Klingons: Star Fleet Intelligence Manual)
By the 22nd century, the nation was known as the Independent Republic of Australia. It was the last of the old nation-states on Earth to join the United Earth government, eventually and reluctantly joining in 2150. (ENT novel: The Good That Men Do, Decipher RPG module: Aliens)
- In the (TNG episode: "Attached"), Beverly Crusher mentioned Australia as a continued hypothetical hold-out against the formation of the United Earth government in 2150. Though only a hypothetical example at the time, it later became fact with The Good That Men Do and Aliens, as above. With Earth Starfleet conducting training there in the 2140s, below, relations were likely to be amicable for some time prior to this.
In the 2140s and in 2150, Earth Starfleet conducted survival training in the Outback of Australia, near Alice Springs. This lasted two weeks and included drinking recycled sweat and eating snake meat. Jonathan Archer, Trip Tucker and A.G. Robinson underwent this training. (ENT episodes: "Desert Crossing", "First Flight")
In an alternate timeline accidentally created by Leonard McCoy saving Edith Keeler's life in March 1930, Australia was conquered by the Empire of Japan prior to 1944. (TOS - Crucible novel: Provenance of Shadows)