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. Neighbouring countries include Indonesia, East Timor and Papua New Guinea to the north, the Solomon Islands, Vanuatu and New Caledonia to the northeast and New Zealand to the southeast.

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. Australia is a member of the United Nations, G20, Commonwealth of Nations, ANZUS, OECD, APEC, Pacific Islands Forum and the World Trade Organization.

Politics
Australia is a constitutional monarchy with a federal division of powers. It uses a parliamentary system of government with Queen Elizabeth II at its apex as the Queen of Australia, a role that is distinct from her position as monarch of the other Commonwealth realms. As the Queen resides in the United Kingdom, the executive powers vested in her by the Constitution are normally exercised by her viceroys in Australia (the Governor-General at the federal level and by the Governors at the state level), who by convention act on the advice of her Ministers. The most notable exercise of the Governor-General's reserve powers outside a Prime Minister's request was the dismissal of the Whitlam Government in the constitutional crisis of 1975.

The federal government is separated into three branches:

The legislature: the bicameral Parliament, comprising the Queen (represented by the Governor-General), the Senate, and the House of Representatives;
The executive: the Federal Executive Council, in practice the Governor-General as advised by the Prime Minister and Ministers of State;
The judiciary: the High Court of Australia and other federal courts, whose judges are appointed by the Governor-General on advice of the Council.
In the Senate (the upper house), there are 76 senators: twelve each from the states and two each from the mainland territories (the Australian Capital Territory and the Northern Territory). The House of Representatives (the lower house) has 150 members elected from single-member electoral divisions, commonly known as "electorates" or "seats", allocated to states on the basis of population, with each original state guaranteed a minimum of five seats. Elections for both chambers are normally held every three years, simultaneously; senators have overlapping six-year terms except for those from the territories, whose terms are not fixed but are tied to the electoral cycle for the lower house; thus only 40 of the 76 places in the Senate are put to each election unless the cycle is interrupted by a double dissolution.

The official residence of the Governor-General of Australia.Australia's electoral system uses preferential voting for all lower house elections with the exception of Tasmania and the ACT, which, along with the Senate and most state upper houses, combine it with proportional representation in a system known as the single transferable vote. Voting is compulsory for all enrolled citizens 18 years and over in every jurisdiction, as is enrolment (with the exception of South Australia). Although the Prime Minister is appointed by the Governor-General, in practice the party with majority support in the House of Representatives forms government and its leader becomes Prime Minister.

There are two major political groups that usually form government, federally and in the states: the Australian Labor Party, and the Coalition which is a formal grouping of the Liberal Party and its minor partner, the National Party. Independent members and several minor parties—including the Greens and the Australian Democrats—have achieved representation in Australian parliaments, mostly in upper houses.

Following a partyroom leadership challenge, Julia Gillard became the first female Prime Minister in June 2010. The last federal election was held on 21 August 2010 and resulted in the first hung parliament in over 50 years. Gillard was able to form a minority Labor government with the support of independents.

States and territories
Australia has six states—New South Wales, Queensland, South Australia, Tasmania, Victoria, and Western Australia—and two major mainland territories—the Northern Territory and the Australian Capital Territory (ACT). In most respects these two territories function as states, but the Commonwealth Parliament can override any legislation of their parliaments. By contrast, federal legislation overrides state legislation only in areas that are set out in Section 51 of the Australian Constitution; state parliaments retain all residual legislative powers, including those over schools, state police, the state judiciary, roads, public transport, and local government, since these do not fall under the provisions listed in Section 51.

Each state and major mainland territory has its own parliament—unicameral in the Northern Territory, the ACT, and Queensland, and bicameral in the other states. The states are sovereign entities, although subject to certain powers of the Commonwealth as defined by the Constitution. The lower houses are known as the Legislative Assembly (the House of Assembly in South Australia and Tasmania); the upper houses are known as the Legislative Council. The head of the government in each state is the Premier, and in each territory the Chief Minister. The Queen is represented in each state by a Governor; and in the Northern Territory, the Administrator. In the Commonwealth, the Queen's representative is the Governor-General.

The federal parliament directly administers the following territories:

Jervis Bay Territory, a naval base and sea port for the national capital in land that was formerly part of New South Wales
Christmas Island and Cocos (Keeling) Islands
Ashmore and Cartier Islands
Coral Sea Islands
Heard Island and McDonald Islands
Australian Antarctic Territory
Norfolk Island is also technically an external territory; however, under the Norfolk Island Act 1979 it has been granted more autonomy and is governed locally by its own legislative assembly. The Queen is represented by an Administrator, currently Owen Walsh.

Geography and climate
Climatic zones in Australia, based on the Köppen climate classification.Australia's landmass of 7,617,930 square kilometres (2,941,300 sq mi) is on the Indo-Australian Plate. Surrounded by the Indian and Pacific oceans, it is separated from Asia by the Arafura and Timor seas. The world's smallest continent and sixth largest country by total area, Australia—owing to its size and isolation—is often dubbed the 'island continent' and variably considered the world's largest island. Australia has 34,218 kilometres (21,262 mi) of coastline (excluding all offshore islands) and claims an extensive Exclusive Economic Zone of 8,148,250 square kilometres (3,146,060 sq mi). This exclusive economic zone does not include the Australian Antarctic Territory.

Australia, as seen from space.The Great Barrier Reef, the world's largest coral reef, lies a short distance off the north-east coast and extends for over 2,000 kilometres (1,240 mi). Mount Augustus, claimed to be the world's largest monolith, is located in Western Australia. At 2,228 metres (7,310 ft), Mount Kosciuszko on the Great Dividing Range is the highest mountain on the Australian mainland, although Mawson Peak on the remote Australian territory of Heard Island is taller at 2,745 metres (9,006 ft).

Australia is the flattest continent, with the oldest and least fertile soils; desert or semi-arid land commonly known as the outback makes up by far the largest portion of land. The driest inhabited continent, only its south-east and south-west corners have a temperate climate. The population density, 2.8 inhabitants per square kilometre, is among the lowest in the world, although a large proportion of the population lives along the temperate south-eastern coastline.

Eastern Australia is marked by the Great Dividing Range that runs parallel to the coast of Queensland, New South Wales and much of Victoria – although the name is not strictly accurate, as in parts the range consists of low hills and the highlands are typically no more than 1,600 metres (5,249 ft) in height. The coastal uplands and a belt of Brigalow grasslands lie between the coast and the mountains while inland of the dividing range are large areas of grassland. These include the western plains of New South Wales and the Einasleigh Uplands, Barkly Tableland and the Mulga Lands of inland Queensland. The northern point of the east coast is the tropical rainforested Cape York Peninsula.

The landscapes of the northern part of the country, the Top End and the Gulf Country behind the Gulf of Carpentaria, with their tropical climate, consist of woodland, grassland and desert. At the northwest corner of the continent is the sandstone cliffs and gorges of The Kimberley and below that the Pilbara while south and inland of these lie more areas of grassland, the Ord Victoria Plain and the Western Australian Mulga shrublands. The heart of the country is the uplands of central Australia while prominent features of the centre and south include the inland Simpson, Tirari and Sturt Stony, Gibson, Great Sandy, Tanami and Great Victoria Deserts with the famous Nullarbor Plain on the southern coast.

The climate of Australia is significantly influenced by ocean currents, including the Indian Ocean Dipole and the El Niño-Southern Oscillation, which is correlated with periodic drought, and the seasonal tropical low pressure system that produces cyclones in northern Australia. These factors induce rainfall to vary markedly from year to year. Much of the northern part of the country has a tropical predominantly summer rainfall (monsoon) climate. Just under three quarters of Australia lies within a desert or semi-arid zone. The southwest corner of the state has a Mediterranean climate. Much of the southeast (including Tasmania) is temperate.