Australia, officially the Commonwealth of Australia, is a 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. Australia's population of nearly 26 million. The official language is English.

It is highly urbanised and heavily concentrated on the eastern seaboard. Canberra is the nation's capital, while the largest city is Sydney, and other major metropolitan areas are Melbourne, Brisbane, Perth, and Adelaide. Indigenous Australians inhabited the continent for about 65,000 years. The earliest known manifestations of the geologic record of the Australian continent are 4.4-billion-year-old.

Australia is the oldest, flattest, and driest inhabited continent, with the least fertile soils. Australia is a highly developed country, with the world's twelfth-largest economy. It has a high-income economy, with the world's tenth-highest per capita income. Australia is a regional power, and has the world's thirteenth-highest military expenditure. The most important economic and cultural centres of Australia are Sydney and Melbourne.

Australia ranks highly in quality of life, health, education, economic freedom, civil liberties, and political rights. It is a member of the United Nations, the G20, the Commonwealth of Nations, the ANZUS, the OECD, the WTO, the APEC, the Pacific Islands Forum, and the ASEAN + 6 mechanism.