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. Its population of nearly 26 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 is the oldest, flattest, and driest inhabited continent, with the least fertile soils. It 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 and climates, with deserts in the centre, tropical rainforests in the north-east, and mountain ranges in the south-east. Australia generates its income from various sources, including mining-related exports, telecommunications, banking, manufacturing, and international education.
Australia is a developed country, with the world's thirteenth-largest economy and tenth-highest per capita income. It is considered a regional power and has the world's thirteenth-highest military expenditure. Immigrants account for 30% of the population, the highest proportion in any country with a population over 10 million. The country ranks highly in measures of health, education, economic freedom, and civil liberties.
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.