William V of Hesse-Kassel (February 13, 1602 – September 21, 1637) was the Landgrave of Hesse-Kassel in the Holy Roman Empire from 1627 to 1637. William was born in Kassel as the son of Maurice, Landgrave of Hesse-Kassel, and of his wife Agnes of Solms-Laubach. Agnes died shortly after the birth of William and his father subsequently married Juliane of Nassau-Dillenburg. After losing much of the Hesse-Kassel territory to the Darmstadt line, and leaving the family in financial ruin, Maurice abdicated in favor of his son.