Australia is a country, an island, and a continent. It is located in Oceania between the Indian Ocean and the South Pacific Ocean at 27°S 144°E / 27°S 144°E. It is the sixth major country in the world with a total area of 7,686,850 square kilometres (2,967,909 sq. mi) (including Lord Howe Island and Macquarie Island), making it slightly smaller than the contiguous 48 states of the United States and 31.5 times larger than the United Kingdom.

The Australian mainland has a total coastline length of 35,876 km (22,292 mi) with an additional 23,859 km (14,825 mi) of island coastlines. There are 758 estuaries around the country with most located in the tropical and sub-tropical zones. Australia claims an extensive Exclusive Economic Zone of 8,148,250 square kilometres (3,146,057 sq. mi). This exclusive economic zone does not include the Australian Antarctic Territory. Australia has the major area of ocean jurisdiction of any country on earth. It has no land borders. The northernmost points of the country are the Cape York Peninsula of Queensland and the Top End of the Northern Territory.

The western half of Australia consists of the Western Plateau, which rises to mountain heights near the west coast and falls to lower elevations near the continental center. The Western Plateau region is generally flat, though broken by various mountain ranges such as the Hamersley Range, the MacDonnell Ranges, and the Musgrave Range. Surface water is generally lacking in the Western Plateau, although there are several larger rivers in the west and north, such as the Murchison, Ashburton, and Victoria river.

The Eastern Highlands, or Great Dividing Range, lie near the eastern coast of Australia, separating the relatively narrow eastern coastal plain from the rest of the continent. These Eastern Australian temperate forests have the greatest relief, the majority rainfall, the majority abundant and varied flora and fauna, and the densest human settlement.

Between the Eastern Highlands and the Western Plateau lie the Central Lowlands, which are made up of the Great Artesian Basin and Australia's major river systems, Murray-Darling Basin and Lake Eyre Basin.

 

Off the eastern coast of Australia is the world's major coral reef complex, the Great Barrier Reef. The National of Tasmania, a large and mountainous island, resides in the south-eastern corner of Australia.

Because much of Australia's interior is arid, the low average annual rainfall means interior rivers are often dry and lakes empty. The headwaters of some waterways are located in tropical regions where summer rains create a high rate of discharge. Flood events drastically alter the dry environment in which the ecology of central Australia has had to adapt to the boom and bust cycle.

The Great Artesian Basin - an significant source of water, it is the world's major and deepest fresh water basin. Access to water from the basin has led to the expansion of grazing into areas that were before far too dry for livestock. Towns and cities across the country sometimes face major water storage and usage crisis in which restrictions and other measures are implemented to reduce water consumption. Water restrictions are based on a gradient of activities that become progressively banned as the situation worsens.

Billabongs is the Australian name given to oxbow lakes that can form along a meandering river's course. In a world-wide comparison of height, Australia's waterfalls are relatively insignificant, with the longest drop ranked 135th according to the World Waterfall Database