The Landgraviate of Hesse-Darmstadt was a State of the Holy Roman Empire. It was founded in 1567 after the division from the Landgraviate of Hesse between the four sons of Landgrave Philip I.
Following Philip's death, Hesse was divided into the regions of Hessen-Kassel, Hessen-Marburg, Hessen-Rheinfels and Hessen-Darmstadt. Darmstadt and Kassel had wars to preserve the Marburg heritag. After the Hessian War Large parts of the disputed Upper Hesse territory including Marburg fell to the elder Kassel line, while Hesse-Darmstadt retained Giessen and Biedenkopf. Hesse-Darmstadt entered Napoleon’s Confederation of the Rhine in 1806 and was consequently raised to the status of a grand duchy in that year. Hesse-Darmstadt joined the allies in 1813 and entered the German Confederation in 1815. Some of Hesse-Darmstadt lands ceded to Prussia and Bavaria, after the decided from the Congress of Vienna. In 1871 became Hesse-Darmstadt one of constituent states from the German Empire.
In 1933, during the Third Reich was the city Darmstadt, the first one in Germany, which to force Jewish shops to close. In the WWII, Darmstadt was largely destroyed by air strikes.
After the WWII the territory east of the Rhine was in the U.S. occupation zone and became part of the Land of Hessen, the rest became a part of Rhineland-Palatinate.