John G. Horgan (born 1974) is a Distinguished University Professor of Psychology at Georgia State University in Atlanta, Georgia. He studies involvement and engagement with terrorism, with a focus on disengagement and deradicalisation from terrorist movements. He has been described by the European Eye on Radicalization research group as the "world’s most distinguished expert in the psychology of terrorism". Since 2019, Horgan has been leading a team of researchers funded by the U.S. Department of Homeland Security to research the incel subculture.