Australia, officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands in the Indian and Pacific Oceans.^{[N 4]} Neighbouring countries include Indonesia, East Timorand Papua New Guinea to the north, the Solomon Islands, Vanuatu and New Caledonia to the northeast and New Zealand to the southeast.

For at least 40,000 years before European settlement in the late 18th century, Australia was inhabited by indigenous Australians,^[11] who belonged to one or more of roughly 250 language groups.^[12][13] After discovery by Dutch explorers in 1606, Australia's eastern half was claimed by Britain in 1770 and initially settled through penal transportation to the colony of New South Wales, formally founded on 7 February 1788^[14] (although formal possession of the land had occurred on 26 January 1788). The population grew steadily in subsequent decades; the continent was explored and an additional five self-governing Crown Colonies were established.

On 1 January 1901, the six colonies became a federation and the Commonwealth of Australia was formed. Since Federation, Australia has maintained a stableliberal democratic political system and is a Commonwealth realm. The population is 22 million, with approximately 60 per cent concentrated in and around the mainland state capitals of Sydney, Melbourne, Brisbane, Perth and Adelaide. The nation's capital city is Canberra, in the Australian Capital Territory. Approximately 56 per cent of Australia's population live in either Victoria or New South Wales, and approximately 77 per cent live on the mainland's east coast.

A prosperous developed country, Australia is the world's thirteenth largest economy. Australia ranks highly in many international comparisons of national performance such as human development, quality of life, health care, life expectancy, public education, economic freedom and the protection of civil liberties and political rights.^[15] Australia is a member of the United Nations, G20, Commonwealth of Nations, ANZUS, OECD, APEC, Pacific Islands Forum and theWorld Trade Organization.

New Zealand (Aotearoa in Māori) is an island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island) and numerous smaller islands. The country is situated some 1,500 kilometres (900 mi) east of Australia across the Tasman Sea, and roughly 1,000 kilometres (600 mi) south of the Pacific island nations of New Caledonia, Fiji, and Tonga. Due to its remoteness, it was one of the last lands to be settled by humans. During its long isolation New Zealand developed a distinctive fauna dominated by birds, many of which became extinct after the arrival of humans and introduced mammals. With a mild maritime climate, the land was mostly covered in forest. The country's varied topography and its sharp mountain peaks owe much to the uplift of land and volcanic eruptions caused by the Pacific and Indo-Australian Plates clashing underfoot.