The Landgraviate of Hesse-Kassel (German: Landgrafschaft Hessen-Kassel), spelled Hesse-Cassel during its entire existence, also known as the Hessian Palatinate (German: Hessische Pfalz), was a state of the Holy Roman Empire. The state was created in 1567 when the Landgraviate of Hesse was divided upon the death of Philip I, Landgrave of Hesse. His eldest son William IV inherited the northern half of the Landgraviate and the capital of Kassel. The other sons received the Landgraviates of Hesse-Marburg, Hesse-Rheinfels and Hesse-Darmstadt.
During the Napoleonic reorganisation of the Empire in 1803, the Landgrave of Hesse-Kassel was elevated to an Electorate and Landgrave William IX became an Imperial Elector. Many members of the House of Hesse-Kassel served in the Danish military, gaining high ranks and power in the realm because many Landgraves were married to Danish princesses. Members of the family who are known to have served Denmark-Norway include Prince Frederik of Hesse-Kassel, Prince Frederick of Hesse-Kassel, and Prince Charles of Hesse-Kassel. It had two votes to the Reichstag: one for itself and one for Hersfeld Abbey.
