Emil Hans Willi Hennig (April 20, 1913 – November 5, 1976) was a German biologist who is considered the founder of phylogenetic systematics, also known as cladistics.
In 1945 as a prisoner of war, Hennig began work on his theory of cladistics, which he published in 1950.
With his works on evolution and systematics he revolutionised the view of the natural order of beings.
As a taxonomist, he specialised in dipterans (ordinary flies and mosquitoes).
He is remembered, among other things, for Hennig's progression rule in cladistics, which argues controversially that the most primitive species are found in the earliest, central part of a group's area.