Khieu Samphan, Cambodian academic and politician, 28th Prime Minister of Cambodia

Khieu Samphan also known as Brother Number Four, is a Cambodian former communist politician and economist who was the chairman of the state presidium of Democratic Kampuchea (Cambodia) from 1976 until 1979. As such, he served as Cambodia's head of state and was one of the most powerful officials in the Khmer Rouge movement, although Pol Pot remained the General Secretary in the party.

The prime minister of Cambodia is the head of government of the Kingdom of Cambodia. The prime minister is also the chairman of the Council of Ministers, and represents the government at home and abroad. Under the current constitution, the prime minister is elected to a five-year term, with no limits imposed on the office. Since 1945, there have been 37 prime ministers, including 4 who served in acting capacity.