Frederick William I, Elector of Hesse (Hanau August 20 1802 - Prague january 6 1875) was between 1847 and 1866 the last Elector of Hesse-Kassel.
He was born in 1802 as son of Prince William, later William II, Elector of Hesse, and Princess Augusta of Prussia, daughter of Frederick William II of Prussia.
During the French occupation of Hesse-Kassel (1806-1813) he stayed with his mother in Berlin. The relationship with his father was bad, because of his fathers affair with Emilie Ortlöpp.
Frederick became regent on september 30 1831. Under influence of his minister Ludwig Hassenpflug he conduced a reactionary policy, which made him very impopular. He was forces to give in to the demands of the March Revolution, but reinstated Hassenpflug in 1850 after the revolution had been crushed.
In the Austro-Prussian War (1866) he chose the side of Austria. His capital Kassel was occupied by Prussia and he was transferred as a prisoner to Stettin on June 23. Hessen-Kassel was annexed by Prussia in the same year.
Frederick William never accepted the Prussian dominance over his territory. Even after the creation of the unified German Empire (1871), he tried to regain his throne. He died in 1875.
Frederich William morganatically married on june 26 1831 Gertrud Falkenstein, which he made Countess of Schaumburg (1831) and Hanau (1833). They had nine children: