The Cambodian–Vietnamese War formally ended with the withdrawal of Vietnamese forces from the People's Republic of Kampuchea, a client state it had implemented to overthrow Democratic Kampuchea and the Khmer Rouge.

The Cambodian–Vietnamese War was an armed conflict between the Khmer Rouge-led Democratic Kampuchea and the Socialist Republic of Vietnam. It began in December 1978, with a Vietnamese invasion of Cambodia which toppled the Khmer Rouge and ended in 1989 with the withdrawal of Vietnamese forces from Cambodia. This Cold War conflict was part of the Third Indochina War and Sino-Soviet split with the Soviet Union supporting Vietnam and China supporting the Khmer Rouge.

The People's Republic of Kampuchea (PRK) was a partially recognised state in Southeast Asia which existed from 1979 to 1989. It was a satellite state of Vietnam, founded in Cambodia by the Vietnamese-backed Kampuchean United Front for National Salvation, a group of Cambodian communists who were dissatisfied with the Khmer Rouge due to its oppressive rule and defected from it after the overthrow of Democratic Kampuchea, Pol Pot's government. Brought about by an invasion from Vietnam, which routed the Khmer Rouge armies, it had Vietnam and the Soviet Union as its main allies.

Democratic Kampuchea was the official name of the Cambodian state from 1976 to 1979, under the government of Pol Pot and the Communist Party of Kampuchea (CPK), commonly known as the Khmer Rouge. The Khmer Rouge's capture of the capital Phnom Penh in 1975 effectively ended the United States-backed Khmer Republic of Lon Nol.

Khmer Rouge is the name that was popularly given to members of the Communist Party of Kampuchea (CPK), and by extension to Democratic Kampuchea, which ruled the country between 1975 and 1979. The name was coined in the 1960s by Norodom Sihanouk to describe his country's heterogeneous, communist-led dissidents, with whom he allied after the 1970 Cambodian coup d'état.