William of Nassau may refer to:
William I, Count of Nassau-Siegen (1487–1559), William the Rich William the Silent, count of Nassau (1533–1584); later Willem of Orange Alternative title for Het Wilhelmus, the Dutch national anthem (named after the above) William of Nassau (1601–1627), grandson of the above William of Nassau (1620–1679), son of the above William, Count of Nassau-Siegen (1592–1642) William of Nassau-Weilburg (1792–1839), duke of Nassau William I of the Netherlands (1772–1843), Count of Nassau (1840-1843), Prince of Nassau-Orange-Fulda, Prince of Orange-Nassau