William V may refer to:
- William V, Duke of Aquitaine (969–1030)
- William V of Montpellier (1075–1121)
- William V, Count of Nevers (fl. 1175–1181)
- William V, Marquess of Montferrat (c. 1115–1191)
- William I, Duke of Bavaria (1330–1389), also William V of Holland
- Wilhelm, Duke of Jülich-Cleves-Berg (1516–1592)
- William V, Duke of Bavaria (1548–1626)
- William V, Landgrave of Hesse-Kassel (1602–1637)
- William V, Prince of Orange (1748–1806)
- Possible future regnal name for Prince William, Duke of Cambridge (born 1982), if he succeeds to the throne of the United Kingdom