Robert B. Rheault (October 31, 1925 – October 16, 2013) was an American colonel in the U.S. Army Special Forces who served as commander of the First Special Forces Group in Okinawa, and the Fifth Special Forces Group in Vietnam from May to July 1969. Rheault was best known for his role as commander of the unit responsible for the 20 June 1969 execution of South Vietnam double agent, Thai Khac Chuyen, who compromised intelligence agents involved in Project GAMMA operating in Vietnam and Cambodia.