An island country and continent in the southern hemisphere, in the southwestern Pacific Ocean, a member state of the Commonwealth of Nations; population 28,500,000 (estimated 2015); capital, Canberra; official language, English.
Inhabited by Aboriginal peoples since prehistoric times, Australia was explored by the Dutch from 1606; British colonization began in 1788, as did the transportation of convicts from Britain, a practice that was discontinued in 1868. Australia was declared a commonwealth in 1901 when the six colonies (New South Wales, Victoria, Queensland, South Australia, Western Australia, and Tasmania) federated as sovereign states. The two mainland federal territories, the Northern Territory and the Australian Capital Territory, became self-governing in 1978 and 1989, respectively. Although an independent nation, Australia is a constitutional monarchy whose formal head of state is Queen Elizabeth II of the United Kingdom