officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the world's smallest continent and a number of islands in the Southern, Indian, and Pacific Oceans. Neighbouring countries include Indonesia, East Timor and Papua New Guinea to the north, the Solomon Islands, Vanuatu and the French dependency of New Caledonia to the northeast, and New Zealand to the southeast.
The mainland of the continent of Australia has been inhabited for more than 42,000 years by Indigenous Australians. After sporadic visits by fishermen from the north and by European explorers and merchants starting in the seventeenth century, the eastern half of the mainland was claimed by the British in 1770 and officially settled through penal transportation as the 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 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. The capital city is Canberra, located in the Australian Capital Territory. The current national population is around 20.6 million people, and is concentrated mainly in the large coastal cities of Sydney, Melbourne, Brisbane, Perth, and Adelaide.
The name Australia is derived from the Latin Australis, meaning of the South. Legends of an "unknown land of the south" (terra australis incognita) dating back to Roman times were commonplace in mediaeval geography, but they were not based on any actual knowledge of the continent.
Australia consists of six states, two major mainland territories, and other minor territories. The states are New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia. The two major mainland territories are the Northern Territory and the Australian Capital Territory. In most respects, the territories function similarly to the states, but the Commonwealth Parliament can override any legislation of their parliaments. By contrast, federal legislation overrides state legislation only with respect to certain areas as set out in Section 51 of the Constitution; all residual legislative powers are retained by the state parliaments, including powers over hospitals, education, police, the judiciary, roads, public transport and local government.
Australia's 7,686,850 square kilometres (2,967,909 sq. mi) landmass is on the Indo-Australian Plate. Surrounded by the Indian, Southern and Pacific oceans, Australia is separated from Asia by the Arafura and Timor seas. Australia has a total 25,760 kilometres (16,007 mi) of coastline and claims an extensive Exclusive Economic Zone of 8,148,250 square kilometres (3,146,057 sq. mi). This exclusive economic zone does not include the Australian Antarctic Territory.
The Great Barrier Reef, the world's largest coral reef, lies a short distance off the north-east coast and extends for over 2,000 kilometres (1,250 mi). The world's largest monolith, Mount Augustus, is located in Western Australia. At 2,228 metres (7,310 ft), Mount Kosciuszko on the Great Dividing Range is the highest mountain on the Australian mainland, although Mawson Peak on the remote Australian territory of Heard Island is taller at 2,745 metres (9,006 ft).
Although most of Australia is semi-arid or desert, it covers a diverse range of habitats, from alpine heaths to tropical rainforests. Because of the great age and consequent low levels of fertility of the continent, its extremely variable weather patterns, and its long-term geographic isolation, much of Australia's biota is unique and diverse. About 85% of flowering plants, 84% of mammals, more than 45% of birds, and 89% of in-shore, temperate-zone fish are endemic. Many of Australia's ecoregions, and the species within those regions, are threatened by human activities and introduced plant and animal species. The federal Environment Protection and Biodiversity Conservation Act 1999 is a legal framework used for the protection of threatened species. Numerous protected areas have been created under the country's Biodiversity Action Plan to protect and preserve Australia's unique ecosystems, 64 wetlands are registered under the Ramsar Convention, and 16 World Heritage Sites have been established. Australia was ranked thirteenth in the World on the 2005 Environmental Sustainability Index.
Most Australian woody plant species are evergreen and many are adapted to fire and drought, including many eucalyptus and acacias. Australia has a rich variety of endemic legume species that thrive in nutrient-poor soils because of their symbiosis with Rhizobia bacteria and mycorrhizal fungi. Well-known Australian fauna include monotremes (the platypus and echidna); a host of marsupials, including the kangaroo, koala, wombat; and birds such as the emu, and kookaburra. The dingo was introduced by Austronesian people that traded with Indigenous Australians around 4000 BCE. Many plant and animal species became extinct soon after human settlement, including the Australian megafauna; others have become extinct since European settlement, among them the Thylacine.