Leif Olav Foss (28 August 1899 – 1982) was a Norwegian trade unionist and politician for the Communist Party.
He spent his early working career at sea, and from 1919 as a docks worker at Akers Mekaniske Verksted.
He was organized, first through the Norsk matros- og fyrbøterunion, then through the Union of Iron and Metalworkers, chairing the sub-union Dokkarbeidernes forening from 1922 to 1925.
He became party secretary for trade affairs, and was a delegate at the Red International of Labour Unions Congress in 1930.
He was sent further to many camps, first Lichterfelde, then Hamburg-Fuhlsbüttel, Neuengamme, Hamburg-Fühlsbuttel again, Königswartha, Bautzen, Leipzig and Eisenach.