politician member of the Parliament of Norway
Onarheim served in the position of deputy representative to the Norwegian Parliament from Hordaland, during the terms 1961–1965 and 1965–1969. From August to September 1963, he served as the Minister of Fisheries during the short-lived centre-right cabinet Lyng. Onar Onarheim had two adopted children, Onar Onarheim Junior. and Torunn Onarheim Staurset.
Onarheim was a member of Stord municipality council from 1947 to 1964 and 1979 to 1983, serving as mayor since 1954 and deputy mayor in 1982–1983.