Francis Bagnall Bessac (pronounced bih-ZAK; January 13, 1922 – December 6, 2010) was an American anthropologist who spent much of his life teaching the subject at the University of Montana, where he was appointed to the faculty in 1965.
During the years toward the end of and immediately following World War II, Bessac served with the Office of Strategic Services (O.S.S.) in Western China and Mongolia, and while escaping from Communist Chinese forces in 1950 on their way to Tibet, Bessac was part of a group mistakenly attacked by Tibetan forces in which Central Intelligence Agency spy Douglas Mackiernan was killed, making him the CIA's first agent killed in action.