William III
- William (disambiguation)
- William I, Count of Hainaut
- William I, Duke of Bavaria
- William II, Count of Flanders
- William II, Count of Provence
- William III of England
- William III of Sicily
- William III of the Netherlands
- William III, Count of Burgundy
- William III, Count of Ponthieu
- William III, Count of Toulouse
- William III, Duke of Aquitaine
- William III, Duke of Bavaria
- William III, Earl of Ross
- William III, Giudice of Cagliari
- William III, Landgrave of Thuringia
- William III, Lord of Montpellier
- William III, Marquess of Montferrat
- William V, Count of Angoulême