Robert de Vere, 9th Earl of Oxford (d. 1397) was a favorite companion of Richard II of England. The king created him Marquess of Dublin and Duke of Ireland. He was thus the first marquess, and the first non-royal Duke in England.
The king intended that de Vere become more or less his viceroy in Ireland, but before he had finished raising his troops, he was accused of treason by the Lords Appellant to Richard II, and fled abroad (1387). His titles and estates were forfeited and he died in exile in 1397.
After his death his uncle Aubrey was restored to the family titles and estates, becoming 10th earl of Oxford.
| Preceded by: New Creation | Duke of Ireland | Followed by: Extinct |
| Preceded by: Thomas de Vere | Earl of Oxford | Followed by: Aubrey de Vere |