Gustav Frederick Dertag Betham OBE (11 April 1915 – 31 March 1984), also known by the Samoan name Fereti Misipita, was a Western Samoan politician and diplomat. He served as a member of the Legislative Assembly from 1948 to 1971 and as Minister of Finance from 1961 to 1970. In 1971 he was appointed Secretary General of the South Pacific Commission, a role he held for four years.