John "Jack" Francis Gunion (born 21 July 1943 in Washington, DC) is an American physicist, specializing in theoretical high energy physics. Gunion received in 1965 his bachelor's degree from Cornell University and in 1970 his Ph.D. from the University of California, San Diego. As a postdoc he was from 1970 to 1972 at SLAC and from 1972 to 1973 at the Massachusetts Institute of Technology. From 1973 to 1975 he was an assistant professor at the University of Pittsburgh. In 1978 he moved to the University of California, Davis and remained there, retiring in 2017 as professor emeritus.