The article covers the century-long historical period (from the beginning of 20th Century till the beginning of 21st Century) and is devoted to the position of the French leading left-wing parties towards Russia (the Soviet Union) and its domestic and foreign policy. The author reveals that the “Russian factor” played an important role in pulling apart the French socialists and communists. It fostered their self-identification after the split of the SFIO, though during the renewed unity of the French left (the Popular Front, the years of occupation, 1970-s) positions of the main French parties regarding Russia came closer. The events in Russia (USSR), the socio-economic development of the Russian society, and Moscow foreign policy has always been great interest for the French left forces and left parties activists. The article is based on the study of a wide range of French political sources and scientific historical literature