Eero Haapalainen (27 October 1880 – 27 November 1937) was a Finnish politician, trade unionist and journalist, who was one of the most prominent figures of the Finnish socialist movement in the first two decades of the 1900s.
In the 1918 Finnish Civil War he served as the commander-in-chief of the Red Guards.
After the war, Haapalainen fled to Soviet Russia where he joined the exile Communist Party of Finland and the Communist Party of the Soviet Union.