Ole Martin Siem (6 January 1915 – 3 November 1996) was a Norwegian businessman and World War II resistance member.
He was born in Horten as a son of naval commander Ole Siem (1882–1979) and Marie Augusta Ursin Holm (1888–1961). The family moved to Tromsø, where Siem finished secondary education in 1933. He took his education in shipping engineering at the Norwegian Institute of Technology, graduating in 1938. He also worked one year at Trondhjems Mekaniske Verksted. In February 1939 he married Inger Aagaard (1916-2012); they are the parents of industrialist Kristian Siem. His sister married diplomat Thore Boye, a son of Thorvald Boye, in 1945.
When World War II reached Norway with the Nazi German invasion, Siem fought for his country in the Battle of Hegra Fortress. After the conventional Norwegian armed forces capitulated, Siem returned to his job at Akers Mekaniske Verksted. While working there he became an informant for the secret intelligence organization RMO, which was es