Born in 1613, second son of Ernst Casimir. Becomes baron of Nassau Dietz in 1640 after the death of his brother Hendrik Casimir I at the battle of Hulst. He was also the viceroy of Friesland and Groningin. He dies in 1664.
Copper engraving of Willem Frederik Baron of Nassau Dietz, engraved by Jacobus Houbraken from the original of A Schouman.