| Count Palatine William of Gelnhausen | |
| Noble Family: | House of Wittelsbach |
| Father: | John Charles, Count Palatine of Gelnhausen |
| Mother: | Esther Maria of Witzleben-Elgersburg |
| Birth Date: | 4 January 1701 |
| Birth Place: | Gelnhausen |
| Death Place: | The Hague |
Count Palatine William of Birkenfeld-Gelnhausen (4 January 1701 in Gelnhausen - 25 December 1760 in The Hague) was a titular Count Palatine of Zweibrücken-Birkenfeld and an Imperial Field Marshal.
William was the youngest son of the Count Palatine John Charles of Gelnhausen (1638–1704) from his second marriage, Esther Maria (1665–1725), a daughter of George Frederick, Baron Witzleben of Elgersburg.
William served from 1729 in the Austrian army and was wounded during the Battle of Mollwitz. In 1742, he won a victory against the French general Bouffleur and drove the French from Tein. In 1743, he became General of the Cavalry in the Dutch army. In 1754, he accompanied Emperor Francis I to his coronation in Frankfurt. In the same year, he became imperial field marshal. In 1757 he was appointed governor of Namur.