Louis IX, Landgrave of Hesse-Darmstadt

Louis IX of Hesse-Darmstadt (German: Ludwig; 15 December 1719 – 6 April 1790) was Landgrave of Hesse-Darmstadt from 1768 to 1790. After his military service in the army of Frederick the Great, Louis was involved in freemasonry and interested theosophy and alchemy.