William IV (disambiguation)

William IV (1765–1837; (r. 1830 – 1837)) was King of the United Kingdom of Great Britain and Ireland and concurrently King of Hanover.

William IV may also refer to:
 * William IV, Duke of Aquitaine (937–994)
 * William IV of Provence (died 1030)
 * William IV of Weimar or William, Margrave of Meissen (died 1062)
 * William IV of Montpellier ((r. 1058 – 1068))
 * William IV, Count of Toulouse (c. 1040–1094)
 * William IV, Marquis of Montferrat (c. 1030–1100)
 * William IV, Count of Nevers (c. 1130–1168)
 * William IV of Forcalquier (1130–1208)
 * William IV of Saint Omer (fl. 1157–1191)
 * William IV, Count of Ponthieu (1179–1221)
 * William IV, Count of Jülich (c. 1210–1278)
 * William IV, Lord of Douglas (died 1333)
 * William IV of Holland or William II, Count of Hainaut (1307–1345)
 * William IV of Hainault or William II, Duke of Bavaria (1365–1417)
 * William IV, Lord of Egmont (1412–1483)
 * William IV, Duke of Brunswick-Lüneburg (c. 1425–1503)
 * William IV, Duke of Jülich-Berg (1455–1511)
 * William IV, Princely count of Henneberg-Schleusingen (1478–1559)
 * William IV, Duke of Bavaria (1493–1550)
 * William IV, Landgrave of Hesse-Kassel (1532–1592)
 * William IV, Prince of Orange (1711–1751)
 * William IV, Grand Duke of Luxembourg (1852–1912)