Frithjof Bettum (13 May 1900 - 20 September 1984) was a Norwegian jurist and politician for the Conservative Party.
He was born in Sandar.
He was elected to the Norwegian Parliament from Vestfold in 1945, but was not re-elected. He later served in the position of deputy representative during the term 1950 - 1953.
Bettum was a member of Sandar municipality council from 1928 to 1937 and 1945 to 1955, serving as deputy mayor in 1931 - 1934.
Bettum was one of three partners of Anders Jahres Rederi from 1928 to 1969 and chairman of the trustees of Anders Jahres Humanitære Stiftelse from 1966 to 1978.