The Cocos Islands mutiny was a failed mutiny by Sri Lankan soldiers against British officers, on the Cocos (Keeling) Islands on 8 May 1942, during the Second World War.

The mutineers attempted to seize control of the islands and disable the British garrison. It was claimed that the mutineers also planned to transfer the islands to the Empire of Japan. However, the mutiny was defeated, the mutineers punished, and the three ringleaders executed; the only British Commonwealth servicemen to be executed for mutiny during the Second World War.

The Territory of Cocos (Keeling) Islands (; Cocos Islands Malay: Pulu Kokos (Keeling)) is an Australian external territory in the Indian Ocean, comprising a small archipelago approximately midway between Australia and Sri Lanka and relatively close to the Indonesian island of Sumatra. The territory's dual name (official since the islands' incorporation into Australia in 1955) reflects that the islands have historically been known as either the Cocos Islands or the Keeling Islands.

The territory consists of two atolls made up of 27 coral islands, of which only two – West Island and Home Island – are inhabited. The population of around 600 people consists mainly of Cocos Malays, who mostly practise Sunni Islam and speak a dialect of Malay as their first language. The territory is administered by the Australian federal government's Department of Infrastructure, Transport, Regional Development and Communications as an Australian external territory and together with Christmas Island (which is about 960 kilometres (600 mi) to the east) forms the Australian Indian Ocean Territories administrative grouping. However, the islanders do have a degree of self-government through the local shire council. Many public services – including health, education, and policing – are provided by the state of Western Australia, and Western Australian law applies except where the federal government has determined otherwise. The territory also uses Western Australian postcodes.

The islands were discovered in 1609 by the British sea captain William Keeling, but no settlement occurred until the early 19th century. One of the first settlers was John Clunies-Ross, a Scottish merchant; much of the island's current population is descended from the Malay workers he brought in to work his copra plantation. The Clunies-Ross family ruled the islands as a private fiefdom for almost 150 years, with the head of the family usually recognised as resident magistrate. The British annexed the islands in 1857, and for the next century they were administered from either Ceylon or Singapore. The territory was transferred to Australia in 1955, although until 1979 virtually all of the island's real estate still belonged to the Clunies-Ross family.