Major Leonard Darwin (1850 - 1943) was one of Charles Darwin's sons, and is noted as an active eugenicist.

Darwin pursued a life in the army, and later a life of science and politics before he was persuaded to take over the Eugenics Education Society (later, the British Eugenics Society), after his father's cousin, Sir Francis Galton, died in 1911. Darwin remained president of the society until 1928.

Darwin was extensively involved in eugenic activities. He wrote The Need for Eugenic Reform in 1926, and followed this with the popular What is Eugenics?. In addition to having a large hand in helping organize the International Eugenic Congress', Darwin is noted for mentoring R. A. Fisher, particularly in areas close to neo-Darwinism, genetics, and statistics. Fisher held Darwin in high regard until Darwin's death in 1943, and even dedicated The Genetical Theory of Natural Selection to his mentor.

-Colette Leung and Erna Kurbegovic

• Edwards,A. W. F. (2004). Darwin, Leonard (1850–1943). Oxford Dictionary of National Biography. Oxford University Press; online edn.