Australia is a country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the world's sixth-largest country by total area. Neighbouring countries include 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.
For at least 40,000 years before the first British settlement in the late 18th century, Australia was inhabited by indigenous Australians, who spoke languages grouped into roughly 250 language groups. After the discovery of the continent by Dutch explorers in 1606, Australia's eastern half was claimed by Great Britain in 1770 and initially settled through penal transportation to the colony of New South Wales from 26 January 1788. The population grew steadily in subsequent decades; the continent was explored and an additional five self-governing Crown Colonies were established.
On 1 January 1901, the six colonies federated, forming the Commonwealth of Australia. Since Federation, Australia has maintained a stable liberal democratic political system that functions as a federal parliamentary democracy and constitutional monarchy. The federation comprises six states and several territories. The population of 23.1 million is highly urbanised and heavily concentrated in the eastern states.
Australia is a developed country and one of the wealthiest in the world, with the world's 12th-largest economy. In 2012 Australia had the world's fifth-highest per capita income, Australia's military expenditure is the world's 13th-largest. With the second-highest human development index globally, Australia ranks highly in many international comparisons of national performance, such as quality of life, health, education, economic freedom, and the protection of civil liberties and political rights. Australia is a member of the United Nations, G20, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development (OECD), World Trade Organization, Asia-Pacific Economic Cooperation, and the Pacific Islands Forum.
Australia's landmass of 7,617,930 square kilometres (2,941,300 sq mi) is on the Indo-Australian Plate. Surrounded by the Indian and Pacific oceans, it is separated from Asia by the Arafura and Timor seas, with the Coral Sea lying off the Queensland coast, and the Tasman Sea lying between Australia and New Zealand. The world's smallest continent and sixth largest country by total area, Australia—owing to its size and isolation—is often dubbed the "island continent", and is sometimes considered the world's largest island. Australia has 34,218 kilometres (21,262 mi) of coastline (excluding all offshore islands), and claims an extensive Exclusive Economic Zone of 8,148,250 square kilometres (3,146,060 sq mi). This exclusive economic zone does not include the Australian Antarctic Territory. Excluding Macquarie Island, Australia lies between latitudes 9° and 44°S, and longitudes 112° and 154°E.
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 (1,240 mi). Mount Augustus, claimed to be the world's largest monolith, 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. Even taller are Mawson Peak (at 2,745 metres or 9,006 feet), on the remote Australian territory of Heard Island, and, in the Australian Antarctic Territory, Mount McClintock and Mount Menzies, at 3,492 metres (11,457 ft) and 3,355 metres (11,007 ft) respectively.