In formal terms, Australia is known as the Commonwealth of Australia. It is a sovereign nation that includes the Australian continent's mainland, the island of Tasmania, and a slew of tiny islands. In terms of land area, it is the most populous nation in Oceania and the sixth most populous in the globe. Its population of almost 26 million people lives in an area of 7,617,930 square kilometres (2,941,300 square miles) and is primarily concentrated on the country's eastern coast. Australia has a total land area of 7,617,930 square kilometres (2,941,300 sq mi) and is largely urbanised. Melbourne, Brisbane, Perth, and Adelaide are all significant metropolitan regions in Australia, with Canberra serving as the nation's capital and Sydney serving as its biggest metropolis.
Various waves of Indigenous Australians inhabited the continent starting about 65,000 years ago, prior to the first arrival of Dutch explorers in the early 17th century, who called the continent New Holland. The continent was initially inhabited by Indigenous Australians around 65,000 years ago. On 26 January 1788, the day on which Australia's national day was established, the eastern half of the continent was claimed by Great Britain and originally colonised via convict transportation to the colony of New South Wales. This date has since been designated as Australia's national day. With each passing decade, the population continued to grow gradually, and by 1850, the continent had been explored extensively by European immigrants, with an additional five self-governing crown colonies having been founded. The Commonwealth of Australia was formed on January 1, 1901, when the six colonies united to create the Commonwealth of Australia. Since then, Australia has maintained a stable liberal democratic political system that operates as a federal parliamentary constitutional monarchy, with six states and ten territories as constituent parts of the country.
Australasia is the world's oldest continuously populated continent, as well as its flattest, driest, and least fruitful continent. As a megadiverse nation, it has a diverse range of landforms and climates due to its large size, including deserts in the centre, tropical rainforests in the north-east, and mountain ranges in the south-east. Australasia derives its revenue from a variety of sources, including mining-related exports, telecommunications and information technology, banking and financial services, manufacturing, and international education and training.
Australia is a highly developed nation with the world's twelfth-largest economy, making it the most developed country in the world. It boasts a high-income economy, with the tenth-highest per capita income in the world as a result. With a military budget that ranks thirteenth in the world, Australia is a regional power with significant regional influence. Among the main Western countries, immigrants constitute 30% of the total population, the greatest percentage among the major Western nations. Australia, which has the eighth-highest Human Development Index and the ninth-highest ranked democracy in the world as of 2020, ranks highly in quality of life, health, education, economic freedom, civil liberties, and political rights, with all of its major cities performing exceptionally well in global comparative livability surveys, according to the World Health Organization. It is a member of the United Nations, the G20, the Commonwealth of Nations, the ANZUS and AUKUS alliances, the OECD, the World Trade Organization, the Asia-Pacific Economic Cooperation, the Pacific Islands Forum, the Pacific Community, and the ASEAN + 6 mechanism, among other organisations.