Thordsen is a surname. Notable people with the surname include: Harold Thordsen (1907–1999), American politician, police officer, and football player, brother of Kelly Jakob Thordsen (born 1999), German sprint canoeist Jimmy Thordsen (born 1948), Puerto Rican Olympic baseball player Kelly Thordsen (1917–1978), American actor, brother of Harold William George Thordsen (1879–1932), United States Navy sailor awarded the Medal of Honor