Hesse-Hanau

Hesse-Hanau (German: Hessen-Hanau) was a territory in the Holy Roman Empire. It emerged when the former county of Hanau-Münzenberg became a secundogeniture of Hesse-Kassel in 1760. When the reigning count, William IX, also became landgrave of Hesse-Cassel in 1785, the two governments began to merge, although the process was delayed first by French occupation, and later by incorporation into the French satellite duchy of Frankfurt. The incorporation of Hesse-Hanau with Hesse-Cassel was not completed until 1821.

==Secundogeniture== thumb|William, Hereditary Prince of Hesse-Cassel and Count of Hesse-Hanau. When the hereditary prince of Hesse-Cassel, the later Frederick II, converted to Roman Catholicism, his father, the reigning landgrave William VIII decided to do what he could to limit his son's future realm. He therefore made the county of Hanau-Münzenberg, incorporated with Hesse-Cassel in 1736, a secundogeniture of Hesse-Cassel, transferring it to the oldest son of Frederic, the hereditary count William.