The Commonwealth of Australia is a country in the southern hemisphere comprising the mainland of the world's smallest continent, the major island of Tasmania and a number of other islands in the Indian and Pacific Oceans.

The Australian mainland has been inhabited for more than 42,000 years by Indigenous Australians. The eastern half of Australia was claimed by the British in 1770 and initially settled through penal transportation as part of the colony of New South Wales. As the population grew and new areas were explored, another five largely self-governing Crown Colonies, Queensland, South Australia, Tasmania, Victoria and Western Australia, were established during the 19th century.

On 1 January 1901, the six colonies became a federation, and the Commonwealth of Australia was formed. Since federation, Australia has maintained a stable liberal democratic political system and remains a Commonwealth Realm.

Australia also has three inhabited external territories: Norfolk Island, Christmas Island and Cocos (Keeling) Islands.