A French historian, political sociologist and expert in the far left and Italian political life, since 1999 Marc Lazar has been a Professor of History and Political Sociology at Institut d'études politiques (IEP) in Paris. Since 2000 he has also been head of that institute's l'école doctorale. In addition, he is currently Visiting Professor at Luiss Guido Carli in Rome.

He was part of the first advanced cycle in history at IEP in 1977. He is also head of École des hautes études en sciences sociales. He is a researcher at Centre d'histoire de Sciences Po and an associate researcher at the Italian Centre of International Studies and Research, where he leads a research group on contemporary Italy. He has worked on communism, the complete study of leftwing socialist and social democratic political parties in Western Europe, the relationship between the left and public services in France, and the mutation of democracy in Italy. He is a scholar of political history and sociology and a supporter of a higher degree of conceptualisation in historical research and opening of history to sociology and political science.