The 1955 State of Vietnam referendum determined the future form of government of the State of Vietnam, the nation that was to become the Republic of Vietnam. It was contested by Prime Minister Ngô Đình Diệm, who proposed a republic, and former emperor Bảo Đại, who had abdicated in 1945 and at the time of the referendum held the title of head of state.

The State of Vietnam was a governmental entity in Southeast Asia that existed from 1949 until 1955, first as a member of the French Union and later as a country. The state claimed authority over all of Vietnam during the First Indochina War, although large parts of its territory were controlled by the Democratic Republic of Vietnam.