Khieu Samphan (Khmer: ខៀវ សំផន; born 28 July 1931)[3] is a Cambodian former communist politician and economist who was the chairman of the state presidium of Democratic Kampuchea (Cambodia) from 1976 until 1979.

He is the oldest living former prime minister and the last surviving senior member of the Khmer Rouge following the deaths of Nuon Chea in August 2019[4] and Kang Kek Iew (Duch) in September 2020.

[5] Samphan was born in Svay Rieng Province to Khieu Long, who served as a judge under the French Protectorate government and his wife Por Kong.

[13] Returning from Paris with his doctorate in 1959, Samphan held a law faculty position at the University of Phnom Penh and started L'Observateur, a French-language leftist publication that was viewed with hostility by the government.

[14] Despite this, Samphan was invited to join Prince Norodom Sihanouk's Sangkum, a 'national movement' that operated as the single political party within Cambodia.

Samphan stood as a Sangkum deputy in the 1962, 1964 and 1966 elections, in which the lattermost the rightist elements of the party, led by Lon Nol, gained an overwhelming victory.

[10] In the Cambodian coup of 1970, the National Assembly voted to remove Prince Sihanouk as head of state, and the Khmer Republic was proclaimed later that year.

[21] Historian Ben Kiernan stated that Samphan's protestations (such as he regarded the collectivization of agriculture as a surprise, and his expressions of sympathy for Hu Nim, a fellow member of the CPK hierarchy tortured and killed at Tuol Sleng) betrayed the fundamental "moral cowardice" of a man mesmerized by power but lacking any nerve.

His lawyers, Jacques Vergès and Say Bory, used the defence that while Samphan has never denied that many people in Cambodia were killed, as head of state, he was never directly responsible for any crimes.

The judgment also emphasised that Samphan "encouraged, incited and legitimised" the criminal policies that led to the deaths of civilians "on a massive scale" including the millions forced into labour camps to build dams and bridges and the mass extermination of Vietnamese.