Bjørn Føyn (21 September 1898 – 8 January 1985) was a Norwegian zoologist, especially known for researching the genetics of algae. He was born in Trondhjem as a son of educator and major Anton Christian Føyn (1865–1940) and Olga Barth Nielsen (1870–1959). He finished his secondary education at Trondhjem Cathedral School in 1918, and graduated from the Royal Frederick University with the cand.real. degree in 1927. He was a research assistant from 1923 to 1928 at the Royal Frederick University, and then under Max Hartmann at the Kaiser-Wilhelm-Institut für Biologie from 1929 to 1932. He was also a research fellow in Norway during this period, and from 1932 to 1937 he worked in Bergen. From 1938 to 1968 he was a professor at the University of Oslo. He was elected as a member of the Norwegian