The September 1964 South Vietnamese coup attempt took place before dawn on September 13, 1964, when the ruling military junta of South Vietnam, led by General Nguyễn Khánh, was threatened by a coup attempt headed by Generals Lâm Văn Phát and Dương Văn Đức, who sent dissident units into the capital Saigon. They captured various key points and announced over national radio the overthrow of the incumbent regime. With the help of the Americans, Khánh was able to rally support and the coup collapsed the next morning without any casualties.

South Vietnam, officially the Republic of Vietnam, was a country in Southeast Asia that existed from 1955 to 1975, the period when the capitalist southern portion of Vietnam was a member of the Western Bloc during part of the Cold War after the 1954 division of Vietnam. It first received international recognition in 1949 as the State of Vietnam within the French Union, with its capital at Saigon, before becoming a republic in 1955. South Vietnam was bordered by North Vietnam to the north, Laos to the northwest, Cambodia to the southwest, and Thailand across the Gulf of Thailand to the southwest. Its sovereignty was recognized by the United States and 87 other nations, though it failed to gain admission into the United Nations as a result of a Soviet veto in 1957. It was succeeded by the Republic of South Vietnam in 1975. In 1976, the Republic of South Vietnam and North Vietnam merged to form the Socialist Republic of Vietnam.