Sergey Dmitrievich Mstislavsky (?????'? ???'??????? ???????'?????, born Maslovsky; November 4, 1876, Moscow - April 22, 1943, Irkutsk, USSR) was a Russian Soviet writer, dramatist, publicist, anthropologist, editor and political activist, close to the Left Socialist-Revolutionaries.
In the 1920s and 1930 he authored numerous adventure novels, mostly about the events of the 1905 and 1917 Revolutions and the Russian Civil War (Built on Blood, 1927; The Heavy Cavalry Alliance, 1928; The Partions, 1932; The Eve.