Australia ( ( listen)), 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. Australia's capital is Canberra, and its largest city is Sydney.
For about 60,000 years before the first British settlement in the late 18th century, Australia was inhabited by indigenous Australians, who in documented times have spoken languages classifiable into roughly 250 groups. After the European 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, 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 several territories.
Australia has the world's 13th-largest economy and tenth-highest per capita income (IMF). With the second-highest human development index globally, the country ranks highly in quality of life, health, education, economic freedom, and civil liberties and political rights. Australia is a member of the ASEAN Plus mechanism, 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. The population of 25 million is highly urbanised and heavily concentrated on the eastern seaboard. Australia has the world's 9th largest immigrant population, with immigrants accounting for 26% of the population.Being the flattest and driest inhabited continent, with the oldest and least fertile soils, Australia has a landmass of 7,617,930 square kilometres (2,941,300 sq mi). 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.