Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the largest country in Oceania and the world's sixth-largest country by total area. The neighbouring countries are Papua New Guinea, Indonesia and East Timor to the north; the Solomon Islands and Vanuatu to the north-east; and New Zealand to the south-east. The population of million is highly urbanised and heavily concentrated on the eastern seaboard. Australia's capital is Canberra, and its largest city is Sydney. The country's other major metropolitan areas are Melbourne, Brisbane, Perth and Adelaide.
Australia was inhabited by indigenous Australians for about 60,000 years before the first British settlement in the late 18th century. It is documented that Aborigines spoke languages that can be classified into about 250 groups. After the European exploration of the continent by Dutch explorers in 1606, who named it New Holland, 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, a date which became Australia's national day. The population grew steadily in subsequent decades, and by the 1850s most of the continent had been explored and an additional five self-governing crown colonies established. On 1 January 1901, the six colonies federated, forming the Commonwealth of Australia. Australia has since maintained a stable liberal democratic political system that functions as a federal parliamentary constitutional monarchy, comprising six states and ten territories.
Being the oldest, flattest and driest inhabited continent, with the least fertile soils, Australia has a landmass of 7617930 km2. A megadiverse country, its size gives it a wide variety of landscapes, with deserts in the centre, tropical rainforests in the north-east and mountain ranges in the south-east. A gold rush began in Australia in the early 1850s, which boosted the population of the country. Nevertheless, its population density, 2.8 inhabitants per square kilometre, remains among the lowest in the world. Australia generates its income from various sources including mining-related exports, telecommunications, banking and manufacturing. Indigenous Australian rock art is the oldest and richest in the world, dating as far back as 60,000 years and spread across hundreds of thousands of sites.
Australia is a highly developed country, with the world's 14th-largest economy. It has a high-income economy, with the world's tenth-highest per capita income. It is a regional power, and has the world's 13th-highest military expenditure. Australia has the world's ninth-largest immigrant population, with immigrants accounting for 26% of the population. Having the third-highest human development index and the eighth-highest ranked democracy globally, the country ranks highly in quality of life, health, education, economic freedom, civil liberties and political rights, with all its major cities faring well in global comparative livability surveys. 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, Pacific Islands Forum and the ASEAN Plus Six mechanism.
The name Australia (pronounced in Australian English ) is derived from the Latin Terra Australis ("southern land"), a name used for a hypothetical continent in the Southern Hemisphere since ancient times. When Europeans first began visiting and mapping Australia in the 17th century, the name Terra Australis was naturally applied to the new territories.
Until the early 19th century, Australia was best known as "New Holland", a name first applied by the Dutch explorer Abel Tasman in 1644 (as Nieuw-Holland) and subsequently anglicised. Terra Australis still saw occasional usage, such as in scientific texts. The name Australia was popularised by the explorer Matthew Flinders, who said it was "more agreeable to the ear, and an assimilation to the names of the other great portions of the earth". The first time that Australia appears to have been officially used was in April 1817, when Governor Lachlan Macquarie acknowledged the receipt of Flinders' charts of Australia from Lord Bathurst. In December 1817, Macquarie recommended to the Colonial Office that it be formally adopted. In 1824, the Admiralty agreed that the continent should be known officially by that name. The first official published use of the new name came with the publication in 1830 of The Australia Directory by the Hydrographic Office.
Colloquial names for Australia include "Oz" and "the Land Down Under" (usually shortened to just "Down Under"). Other epithets include "the Great Southern Land", "the Lucky Country", "the Sunburnt Country", and "the Wide Brown Land". The latter two both derive from Dorothea Mackellar's 1908 poem "My Country".