The Landgraviate of Hesse-Kassel (German: Landgrafschaft Hessen-Kassel) was a state in the Holy Roman Empire under Imperial immediacy that came into existence when the Landgraviate of Hesse was divided in 1567 upon the death of Philip I, Landgrave of Hesse.
His eldest son William IV inherited the northern half and the capital of Kassel. The other sons received the Landgraviate of Hesse-Marburg, the Landgraviate of Hesse-Rheinfels and the Landgraviate of Hesse-Darmstadt.
The Landgrave of Hesse-Kassel was elevated to the Electorate of Hesse and Landgrave William IX was elevated to Imperial Elector during the reorganization of the Empire in 1803, in the midst of the Napoleonic wars, and later occupied by French troops and became part of the Kingdom of Westphalia, which was a French satellite state.
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