Frederick William (German: Friedrich Wilhelm) was Elector of Brandenburg and Duke of Prussia, thus ruler of Brandenburg-Prussia, from 1640 until his death in 1688. A member of the House of Hohenzollern, he is popularly known as "the Great Elector" (der Große Kurfürst) because of his military and political achievements. Frederick William was a staunch pillar of the Calvinist faith, associated with the rising commercial class. He saw the importance of trade and promoted it vigorously. His shrewd domestic reforms gave Prussia a strong position in the post-Westphalian political order of north-central Europe, setting Prussia up for elevation from duchy to kingdom, achieved under his son and successor.
Elector Frederick William was born in Berlin to George William, Elector of Brandenburg, and Elisabeth Charlotte of the Palatinate. His inheritance consisted of the Margraviate of Brandenburg, the Duchy of Cleves, the County of Mark, and the Duchy of Prussia.