Major Leonard Darwin (15 January 1850 — 26 March 1943) was the fourth son and eighth child of Charles and Emma Darwin.

He joined the Royal Engineers in 1871. Between 1877 and 1882 he worked for the Intelligence division of the Ministry of War. In 1890 was promoted to the rank of Major. Between 1892 and 1895 he was a Liberal MP for Lichfield, Staffordshire.

He married Elizabeth Fraser in July of 1882. Later he married Charlotte Mildred Massingberd (1868–1940), but had no children from either marriage.

He was Chairman of the British Eugenics Society between 1911-1928, (succeeding his cousin once removed Francis Galton), and became Honorary President from 1928 until his death. He was an officer of the Royal Geographical Society from 1908 to 1911, and then its president

He corresponded with and mentored the geneticist and statistician Ronald Fisher, their correspondance can be found here http://www.library.adelaide.edu.au/digitised/fisher/natsel/index.html . Fisher's 1930 book The Genetical Theory of Natural Selection is dedicated to him.

	Topics relating to Charles Darwin
	Family: Erasmus Darwin (grandfather) - Josiah Wedgwood (maternal grandfather) - Emma Darwin (wife) - William Darwin; Anne Darwin; Etty Darwin; George Darwin; Elizabeth Darwin; Francis Darwin; Leonard Darwin; Horace Darwin; Charles Waring Darwin (children) - Francis Galton (cousin)
	Contributions to evolutionary biology: Evolution by means of natural and Censored page.
	Books: The Voyage of the Beagle - The Origin of Species - Censored page
	Named in honour of Darwin: Darwin Medal - Darwin, Australia - Charles Darwin University, Darwin College, Cambridge