William, Duke of Jülich-Cleves-Berg (1516-1592), was a German nobleman known for his role in the political landscape of the Holy Roman Empire. He was the son of John III, Duke of Jülich-Cleves-Berg and inherited the duchy in 1548. His reign was marked by efforts to strengthen his territories and navigate the complex relationships among European powers. William was also notable for his involvement in the Reformation, as he supported Protestantism in a predominantly Catholic region. His policies and alliances influenced the balance of power in Northwest Germany during the late 16th century, contributing to the region's historical significance.