New South Wales (commonly abbreviated as NSW) is a state on the east coast of Australia. It borders Queensland to the north, Victoria to the south, and South Australia to the west. Its coast borders the Coral and Tasman Seas to the east. The Australian Capital Territory and Jervis Bay Territory are enclaves within the state. New South Wales' state capital is Sydney, which is also Australia's most populous city. In December 2021, the population of New South Wales was over 8 million, making it Australia's most populous state. Just under two-thirds of the state's population, 5.3 million, live in the Greater Sydney area.

The Colony of New South Wales was founded as a British penal colony in 1788. It originally comprised more than half of the Australian mainland with its western boundary set at 129th meridian east in 1825. The colony then also included the island territories of Van Diemen's Land, Lord Howe Island, and Norfolk Island. During the 19th century, most of the colony's area was detached to form separate British colonies that eventually became the various states and territories of Australia. However, the Swan River Colony was never administered as part of New South Wales.

Lord Howe Island remains part of New South Wales, while Norfolk Island has become a federal territory, as have the areas now known as the Australian Capital Territory and the Jervis Bay Territory.