William (4 July 1535 – 20 August 1592), called William the Younger (German: Wilhelm der Jüngere), was Duke of Brunswick-Lüneburg and Prince of Lüneburg from 1559 until his death.

William was the third son of Ernest I, Duke of Brunswick-Lüneburg.

[1] On 12 October 1561 he married Dorothea of Denmark (29 June 1546 Kolding–6 January 1617 Winsen),[2] daughter of Christian III of Denmark and Dorothea of Saxe-Lauenburg.

These fits caused his wife to flee him in 1584 for her own safety.

After William's death, his wife became regent for their son George.