Louis VIII (German: Ludwig; 5 April 1691 – 17 October 1768) was the Landgrave of Hesse-Darmstadt from 1739 to 1768. He was the son of Ernest Louis, Landgrave of Hesse-Darmstadt and Margravine Dorothea Charlotte of Brandenburg-Ansbach.
In 1717, he was married to his maternal first cousin's daughter, Countess Charlotte Christine of Hanau-Lichtenberg and he received Hanau-Lichtenberg as an addition to his dominions. His mistress was Helena Martini. Because of his passion for hunting, he is known as the "Hunting Landgrave" (German: Jagdlandgraf). During the Seven Years' War he stood on the side of the Emperor and received the rank of General Field Marshal.
Like his father, Louis was not a gifted economist and only his good relationship with Empress Maria Theresa and her intervention at the Imperial Court Council kept the Landgraviate from bankruptcy. However, his caring for his country is documented by the establishment of a textile house in 1742 and a state orphanage in the 1746.
Landgrave Louis IX, married in 1741 Countess Palatine Caroline of Zweibrücken, had issue
Prince George William, married in 1748 Countess Maria Louise Albertine of Leiningen-Dagsburg-Falkenburg, had issue
Princess Caroline Louise; married in 1751 Charles Frederick, Margrave of Baden, later first Grand Duke of Baden, had issue
The Age of Absolutism in Hesse-Darmstadt (German)
Die Geschichte Hessens, Gerd Bauer, Heiner Boencke, Hans Sarkowicz; Eichborn, 2002, p. 193-194