William I, Prince of Orange (24 April 1533 – 10 July 1584), also widely known as William the Silent (Dutch: Willem de Zwijger), or simply William of Orange (Dutch: Willem van Oranje), is the main leader of the Dutch revolt against the Spanish that sets off the Eighty Years' War and results in the formal independence of the United Provinces in 1648.

Born into the House of Nassau as a count of Nassau-Dillenburg, he becomes Prince of Orange in 1544 and is thereby the founder of the branch House of Orange-Nassau.

A wealthy nobleman, William originally serves the Habsburgs as a member of the court of Margaret of Parma, governor of the Spanish Netherlands.

Unhappy with the centralization of political power away from the local estates and with the Spanish persecution of Dutch Protestants, William joins the Dutch uprising and turns against his former masters.

The most influential and politically capable of the rebels, he leads the Dutch to several successes in the fight against the Spanish.

Declared an outlaw by the Spanish king in 1580, he is assassinated by Balthasar Gérard (also written as 'Gerardts') in Delft four years later.