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.

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.