The Landgraviate of Hessen-Kassel or Hesse-Cassel was a reichsfreie principality of the Holy Roman Empire that came into existence when the Landgraviate of Hesse was divided in 1567 upon the death of Philip I, Landgrave of Hesse. The Landgraviate of Hesse-Kassel expanded in 1604 when Maurice, Landgrave of Hesse-Kassel, inherited the Landgraviate of Hesse-Marburg from his childless uncle, Louis IV, Landgrave of Hesse-Marburg (1537–1604).