Reo Franklin Fortune (27 March 1903 – 25 November 1979) was a New Zealand-born social anthropologist.
Originally trained as a psychologist, Fortune was a student of the major theorists of British and American social anthropology including Alfred Cort Haddon, Bronislaw Malinowski and Alfred Radcliffe-Brown.
He lived an international life, holding various academic and government positions in China (Lingnan University; 1937–39), the United States (Toledo; 1940–41), Canada (Toronto; 1941–43), Burma (government anthropologist;
1946–47), and finally, in the United Kingdom as lecturer in social anthropology at Cambridge University from 1947 to 1971, as a specialist in Melanesian language and culture.He was first married to Margaret Mead in 1928, with whom he undertook field studies in New Guinea from 1931 to 1933.
They divorced in 1936.
Fortune subsequently married Eileen Pope, also a New Zealander, in 1937.Fortune provided significant insights into the consequences of matrilateral and patrilateral cross-cousin marriage in advance of work by Claude Levi-Strauss.
He is also known for his contribution to mathematics with his study of Fortunate numbers in number theory.The 2014 novel Euphoria by Lily King is a fictionalized account of the relationships between Fortune, Mead and Gregory Bateson in pre-WWII New Guinea.