Khieu Samphan (born July 27, 1931) was the president of the state presidium of Democratic Kampuchea (Cambodia) from 1976 until 1979. As such, he served as the country's head of state and was one of the most powerful officials in the Khmer Rouge movement, though Pol Pot was the group's true political leader and held the most extensive power. Khieu is of Chinese-Khmer ancestry.

A prominent member of the circle of leftist Khmer intellectuals studying in Paris in the 1950s, Khieu Samphan studied economics and politics there. His successful 1959 doctoral thesis, "Cambodia's Economy and Industrial Development" advocated national self-reliance and generally sided with dependency theorists in blaming the wealthy, industrialized states for the poverty of the Third World. He was one of the founders of the Khmer Students' Association (KSA), out of which would grow the left-wing revolutionary movements that would so alter Cambodian history in the 1970s, most notably the Khmer Rouge. Once the KSA was shuttered by French authorities in 1956, he founded yet another student organization, the Khmer Students' Union.

Returning from Paris with his doctorate in 1959, Khieu held a 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. His first important conflict with the anti-Communist Cambodian authorities came the following year, when L'Observateur was banned and Khieu was arrested, forced to undress and photographed in public.