William VI

William VI may refer to:


 * William VI, Duke of Aquitaine (1004–1038)
 * William VI, Count of Auvergne (1096–1136)
 * William VI of Montpellier (before 1120–after 1161)
 * William VI, Marquess of Montferrat (c. 1173–1226)
 * William II, Duke of Bavaria (died 1417), also William VI of Holland
 * William the Younger, Duke of Brunswick-Lüneburg (1535–1592)
 * William VI, Landgrave of Hesse-Kassel (or Hesse-Cassel) (1629–1663)
 * William I of the Netherlands (1772–1843), also William VI of Orange