Tatu Kolehmainen (21 April 1885 – 15 June 1967) was a Finnish long-distance runner who competed at the 1912 and 1920 Summer Olympics. In 1912, he reached the finals of 10,000 m and marathon races, but failed to finish due to a strong heat. In 1920, he placed 10th in the marathon. His younger brother Hannes competed alongside at the 1912 and 1920 Games.