George William, of the Hohenzollern dynasty, was Margrave and Elector of Brandenburg and Duke of Prussia from 1619 until his death. His reign was marked by ineffective governance during the Thirty Years' War. He was the father of Frederick William, the "Great Elector".

The Duchy of Prussia or Ducal Prussia was a duchy in the region of Prussia established as a result of secularization of the Monastic Prussia, the territory that remained under the control of the State of the Teutonic Order until the Protestant Reformation in 1525.