Landgrave William of Hesse-Kassel (1743-1821) was a German nobleman and a member of the House of Hesse. He ruled the Landgraviate of Hesse-Kassel from 1751 until his death, overseeing a period of significant economic and cultural development in the region. William was known for his interest in the arts and sciences, which contributed to the advancement of education and infrastructure in Hesse-Kassel. William was also notable for his military involvement, particularly during the American Revolutionary War, where he supported the British by sending troops. His actions during this conflict had lasting implications for the relationship between Germany and the United States.