Harold Holt, Prime Minister of Australia, disappears while swimming near Portsea, Victoria, and is presumed drowned.

Harold Edward Holt was an Australian politician and lawyer who served as the 17th prime minister of Australia from 1966 until his disappearance and presumed death in 1967. He held office as leader of the Liberal Party of Australia and held various ministerial positions from 1949 to 1966 in the governments of Robert Menzies and Arthur Fadden. He was the first Australian prime minister to be born after federation.

The prime minister of Australia is the head of government of the Commonwealth of Australia. The prime minister is the chair of the Cabinet of Australia and thus the head of the federal executive government. Under the principles of responsible government, the prime minister is both responsible to and a member of the Commonwealth Parliament. The current prime minister is Anthony Albanese of the Australian Labor Party, who assumed the office on 23 May 2022.

On 17 December 1967, Harold Holt, the 17th prime minister of Australia, disappeared while swimming in the sea near Portsea, Victoria. An enormous search operation was mounted in and around Cheviot Beach, but his body was never recovered. Holt was presumed to have drowned, and his memorial service five days later was attended by many world leaders.

Portsea is a seaside suburb on the Mornington Peninsula in Melbourne, Victoria, Australia, approximately 60 kilometres (37 mi) south-west of Melbourne's Central Business District, located within the Shire of Mornington Peninsula local government area. Portsea recorded a population of 787 at the 2021 census.