Seymour Martin Lipset (March 18, 1922 – December 31, 2006) was an American political sociologist, a senior fellow at the Hoover Institution at Stanford University, and the Hazel Professor of Public Policy at George Mason University. His major work was in the fields of political sociology, trade union organization, social stratification, public opinion, and the sociology of intellectual life. He also wrote extensively about the conditions for democracy in comparative perspective.