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. Australia is the largest country by area in Oceania and the world's sixth-largest country. Australia is the oldest, flattest, and driest inhabited continent, with the least fertile soils. It is a megadiverse country, and its size gives it a wide variety of landscapes and climates, with deserts in the centre, tropical rainforests in the north-east, tropical savannas in the north, and mountain ranges in the south-east.

Australia is a federal parliamentary constitutional monarchy, comprising six states and ten territories. Australia's population of nearly 26 million is highly urbanised and heavily concentrated on the eastern seaboard. Canberra is the nation's capital, while its most populous city and financial centre is Sydney. The next four largest cities are Melbourne, Brisbane, Perth, and Adelaide. It is ethnically diverse and multicultural, the product of large-scale immigration, with almost half of the population having one parent born overseas. Australia's abundant natural resources and well-developed international trade relations are crucial to the country's economy, which generates its income from various sources including services, mining exports, banking, manufacturing, agriculture and international education. Australia ranks amongst the highest in the world for quality of life, health, education, economic freedom, civil liberties and political rights.

Australia has a highly developed market economy and one of the highest per capita incomes globally.