King George Island is the largest of the South Shetland Islands, lying 120 km (75 miles) off the coast of Antarctica in the Southern Ocean. The island was named after King George III.

The island was first claimed for Britain on 16 October 1819, formally annexed by Britain as part of the Falkland Islands Dependencies in 1908, and now as part of the separate British Antarctic Territory. The Island was claimed by Chile in 1940, as part of the Chilean Antarctic Territory. It was also claimed by Argentina in 1943, now as part of Argentine Antarctica, called by the Argentines Isla Veinticinco de Mayo (25 May) in honour of their National Day. The US and Russia do not recognize any Antarctic claim, and have formally reserved their right to claim Antarctic territories.

The island was discovered and named by the British explorer William Smith in 1819, who named it after the then King, George III. It is approximately 95 km (59 mi) long and 25 km (16 mi) wide with a land area of 1,150 square kilometres (444 sq mi). Over 90% of the island's surface is permanently glaciated. In 1821, 11 men of the sealing vessel Lord Melville survived the winter on the island, the first men to do so in Antarctica.