William IV

William IV may refer to:

• William IV of the United Kingdom (1765–1837)
• William IV, Duke of Aquitaine (937–994)
• William IV of Provence (died 1030)
• William, Margrave of Meissen (died 1062), also William IV of Weimar
• William IV, Count of Toulouse (c. 1040–1094)
• William IV, Marquess of Montferrat (1030–1100)
• William IV, Count of Nevers (1130–1168)
• William IV, Count of Ponthieu (1179–1221)
• William IV, Count of Jülich (c. 1210 – 1278)
• William IV, Lord of Douglas (died 1333)
• William II, Count of Hainaut (1307–1345), also William IV of Holland
• William II, Duke of Bavaria (ruled 1404–1417), also William IV of Hainault
• William IV, Duke of Brunswick-Lüneburg (c. 1425–1503)
• William IV, Duke of Bavaria (1493–1550)
• William, Duke of Jülich-Cleves-Berg (1516–1592)
• William IV, Landgrave of Hesse-Kassel (or Hesse-Cassel) (1532–1592)
• William IV, Prince of Orange (1711–1751)
• William IV, Grand Duke of Luxembourg (1852–1912)