Alfred Rosmer (1877–1964) was a syndicalist leader before World War I and one of the few leaders of that movement to oppose the war from a revolutionary internationalist position.
A friendship with Leon Trotsky dated from that period, when the latter was living in France. After the war he became a leading figure in the Communist Party of France before being ousted as early as 1924, along with Boris Souvarine and Pierre Monatte, for opposing Stalinism and the elimination of the Old Bolsheviks, as that party underwent so called "Bolshevisation". He then became a leader of the early Trotskyist movement only to drop out of politics in 1932.
Nevertheless he remained a convinced revolutionary and his friendship with Trotsky was later repaired. The founding congress of the Trotskyist Fourth International was held at his home outside Paris.
Rosmer was a member of the Dewey Commission which cleared Trotsky of all charges made during the Moscow Trials.
- Lenin's Moscow
- Trotsky and the Origins of Trotskyism