Heng Samrin (Khmer: ហេង សំរិន; born 25 May 1934) is the President of the National Assembly of Cambodia, Honorary President of the Cambodian People's Party (CPP), and a Member of Parliament for Kampong Cham Province. He previously served as the de facto leader of the Hanoi-backed People's Republic of Kampuchea from 1979 to 1981 and General Secretary of the Kampuchean People's Revolutionary Party (the CPP's former name) from 1981 to 1991. Heng Samrin is Cambodia's oldest parliamentarian, at 81 years of age. His honorary title is "Samdech Akeak Moha Ponhea Chakrei Heng Samrin" (Khmer: សម្តេចអគ្គមហាពញាចក្រី ហេង សំរិន).
Heng Samrin was born in Kampong Cham Province, Cambodia, in 1934. He joined the Khmer Rouge communist movement led by Pol Pot, and became a political commissar and army division commander when the Khmer Rouge, backed by China, took over the government in 1975. In 1978, after a series of violent purges within the Khmer Rouge leadership in which many prominent cadre members whom Pol Pot felt might be rivals were executed, he fled to Vietnam. In Vietnam he was one of the founding members of the Kampuchean United Front for National Salvation (FUNSK). Later that year, Heng returned to Cambodia and organized a resistance movement with the backing and support of Vietnam and the Soviet Union.