William of Jülich-Cleves-Berg (I of Cleves, V of Jülich-Berg) (German: Wilhelm der Reiche; July 28, 1516 – January 5, 1592) is a Duke of Jülich-Cleves-Berg (1539-1592).

William was born in and dies in Düsseldorf.

He is the only son of John III, Duke of Jülich-Cleves-Berg, and Maria, Duchess of Jülich-Berg.

William takes over rule of his father's estates (the Duchy of Cleves and the County of Mark) upon his death in 1539.

Despite his mother having lived until 1543, William also becomes the Duke of Berg and Jülich and the Count of Ravenstein.