Hun Sen (Khmer: ហ៊ុន សែន) (born August 5, 1952; officially on April 4, 1951) is the Prime Minister of Cambodia.

He is one of the key leaders of the Cambodian People's Party (CPP), which has governed Cambodia since the Vietnamese-backed overthrow of the Khmer Rouge in 1979. He was a former Khmer Rouge who escaped to Vietnam before 1979 in order to call the Vietnamese to overthrow the other Khmer Rouge. Since the restoration of multi-party democracy in 1993, the CPP has been in coalition with the royalist Funcinpec party and as senior partner since 1997.

His current, full, honorary title is: Samdach Akkak Moha Sena Padey Dekjo Hun Sen. The title "Samdech" was attached to his name in 1993 by King Norodom Sihanouk. It is only an honorary title and does not give him further powers. He has a glass eye, the result of a wound sustained during the Khmer Rouge offensive against Phnom Penh in April 1975.