South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of 983,482 square kilometres (379,725 sq mi), it is the fourth largest of Australia's six states and two territories.

South Australia shares borders with all of the mainland states and the Northern Territory. It is bordered to the west by Western Australia, to the north by the Northern Territory, to the north-east by Queensland, to the east by New South Wales, to the south-east by Victoria, and to the south by the Great Australian Bight and the Indian Ocean. With over 1.6 million people, the state comprises less than 8% of the Australian population and ranks fifth in population among the states and territories. The majority of its people reside in the state capital, Adelaide, with most of the remainder settled in fertile areas along the south-eastern coast and River Murray. The state's origins are unique in Australia as a freely-settled, planned British province, rather than as a convict settlement. Official settlement began on 28 December 1836, when the colony was proclaimed at The Old Gum Tree by Governor John Hindmarsh.

The first settlement to be established was Kingscote, Kangaroo Island, in July 1836, five months before Adelaide was founded. The guiding principle behind settlement was that of systematic colonisation, a theory espoused by Edward Gibbon Wakefield that was later employed by the New Zealand Company. The aim was to establish the province as a centre of civilisation for free immigrants, promising civil liberties and religious tolerance. Although its history is marked by economic hardship, South Australia has remained politically innovative and culturally vibrant. Today, the state is known as a state of festivals and of fine wine. The state's economy centres on the agricultural, manufacturing and mining industries and has an increasingly significant finance sector as well.

Evidence for human activity in South Australia dates back as far as 20,000 years ago with flint mining activity and rock art in the Koonalda Cave on the Nullarbor Plain. In addition wooden spears and tools were made in an area now covered in peat bog in the South East. Kangaroo Island was inhabited long before the island was cut off by rising sea levels.

The first recorded European sighting of the South Australian coast was in 1627 when the Dutch ship the Gulden Zeepaert, captained by Francois Thijssen, examined the coastline. Thijssen named his discovery "Pieter Nuyts Land", after the highest ranking individual on board.

The coastline of South Australia was first mapped by Matthew Flinders and Nicolas Baudin in 1802.

The land which now forms the state of South Australia was claimed for Britain in 1788 as part of the colony of New South Wales. Although the new colony included almost two thirds of the continent, early settlements were all on the eastern coast and only a few intrepid explorers ventured this far west. It took more than forty years before any serious proposal to establish settlements in the south-western portion of New South Wales were put forward. In 1834, the British Parliament passed the South Australia Act 1834 (Foundation Act), which enabled the province of South Australia to be established. The act stated that 802,511 square kilometres (309,851 sq mi) would be allotted to the colony and it would be convict-free. In contrast to the rest of Australia, terra nullius did not apply to the new province. The Letters of Patent attached to the Act acknowledged Aboriginal ownership and stated that no actions could be undertaken that would affect the rights of any Aboriginal natives of the said province to the actual occupation and enjoyment in their own persons or in the persons of their descendants of any land therein now actually occupied or enjoyed by such natives. Although the patent guaranteed land rights under force of law for the indigenous inhabitants it was ignored by the South Australian Company authorities and squatters.

Settlement of seven vessels and 636 people was temporarily made at Kingscote on Kangaroo Island, until the official site of the colony was selected where Adelaide is currently located. The first immigrants arrived at Holdfast Bay (near the present day Glenelg) in November 1836, and the colony was proclaimed on 28 December 1836, now known as Proclamation Day. South Australia is the only Australian state to be settled entirely by free settlers.

The plan for the colony was that it would be the ideal embodiment of the best qualities of British society, that is, no religious discrimination or unemployment and, as it was believed that this would also result in very little crime, no provision was made for a gaol. In early 1838 the colonists became concerned after it was reported that convicts who had escaped from the eastern states may make their way to South Australia. The South Australia Police was formed later that year to protect the community and enforce government regulations and the first gaol, a two roomed hut, was opened on 1 January 1839.

The current flag of South Australia was adopted on 13 January 1904, and is a British blue ensign defaced with the state badge. The badge is described as a Piping Shrike with wings outstretched on a yellow disc. The state badge is believed to have been designed by Robert Craig of Adelaide's School of Design.

South Australia granted restricted women's suffrage in 1861, and in 1895 became the second place in the world to grant universal suffrage (after New Zealand), and the first where women had the dual rights to vote and to stand for election.

The terrain consists largely of arid and semi-arid rangelands, with several low mountain ranges. The most important (but not tallest) is the Mount Lofty-Flinders Ranges system, which extends north about 800 kilometres (497 mi) from Cape Jervis to the northern end of Lake Torrens. The highest point in the state is not in those ranges; Mount Woodroffe (1,435 metres (4,708 ft)) is in the Musgrave Ranges in the extreme northwest of the state. The south-western portion of the state consists of the sparsely-inhabited Nullarbor Plain, fronted by the cliffs of the Great Australian Bight. Features of the coast include Spencer Gulf and the Eyre and Yorke Peninsulas that surround it.

The principal industries and exports of South Australia are wheat, wine and wool. More than half of Australia's wines are produced in the South Australian wine regions which include: Barossa Valley, Clare Valley, McLaren Vale, Coonawarra, Adelaide Hills, Riverland and a number of others – see South Australian wine.

South Australia has boundaries with every other Australian state and territory except the Australian Capital Territory and Tasmania. The area now known as the Northern Territory was annexed to South Australia in 1863, however it was handed over to the federal government in 1911 and became a separate territory. South Australia's south coast is flanked by the Southern Ocean.
 

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