Marcel Cachin (märsĕl´ käshăN´), 1869–1958, French Communist leader. An early leader of the Socialist party, he was instrumental in bringing many Socialists into the first French Communist party in 1920. Long the leader of the Communists in the chamber of deputies and editor of the Communist daily Humanité, he became the first Communist senator in 1935. He was expelled from his seat after the German-Soviet nonaggression pact in Aug., 1939, and was subsequently arrested. In 1945 he was elected to the national assembly, where he sat until his death.