William IX may refer to:
- William IX of Aquitaine (1071–1126)
- William IX, Count of Poitiers (1153–1156)
- William IX of Montferrat (1494–1518)
- Wilhelm, Duke of Jülich-Cleves-Berg (1516–1592)
- William I, Elector of Hesse (or Hesse-Cassel), also known as William IX, Landgrave of Hesse-Kassel, (1743–1821)
See also
- King William (disambiguation)
- Prince William (disambiguation)
- List of people named William#Royalty and nobility
Topics referred to by the same termThis disambiguation page lists articles about people with the same name. If an internal link led you here, you may wish to change the link to point directly to the intended article. Category: