The Commonwealth of Australia is a country in the Southern Hemisphere comprising the world's smallest continent and a number of islands in the Southern, Indian and Pacific Oceans. Australia's neighbouring countries are Indonesia, East Timor and Papua New Guinea to the north, the Solomon Islands, Vanuatu and New Caledonia to the north-east, and New Zealand to the south-east.
The continent of Australia has been inhabited for more than 42,000 years by Aboriginal and Torres Strait Islander peoples. After sporadic visits by European explorers and merchants from the 17th century onwards, the eastern half of the continent was claimed by the British in 1770, and officially settled as the penal colony of New South Wales on 26 January 1788. As the population grew and new areas were explored, another five largely self-governing Crown colonies were successively established over the course of the 19th century.
On 1 January 1901, the six colonies federated and the Commonwealth of Australia was formed. Since federation, Australia has maintained a stable liberal democratic political system and remains a Commonwealth realm. The current population of around 21 million is concentrated mainly in the coastal cities of Sydney, Melbourne, Brisbane, Adelaide and Perth.