The Duke of Jülich was a title held by the rulers of the Duchy of Jülich, a historical region in present-day Germany. The duchy was established in the late Middle Ages and became significant in the political landscape of the Holy Roman Empire. The dukes played a crucial role in regional politics and were involved in various conflicts and alliances. The most notable duke was William the Rich, who ruled in the 16th century and expanded the duchy's influence. The title eventually became part of larger territorial unions, including the {Duchy of Cleves} and the {Duchy of Berg}, leading to the eventual dissolution of the independent duchy.