Sir Robert de Umfraville KG, Lord of Redesdale (c. 1363 – 1437) was a knight in late-medieval England who took part in the later stages of the Hundred Years' War, particularly against Scotland. The de Umfraville family had been influential in northeast England for centuries and also held major estates in Yorkshire. His ancestors were mormaers of Angus, and his nephew married into the Percies, a powerful local marcher family with whom de Umfraville was closely associated. Much of Sir Robert's career continued on the same path as his ancestors, being primarily focused on defending the border with Scotland, which had been in a state of near-permanent warfare since the late thirteenth century.
Robert de Umfraville fought under three English kings. Beginning his career under Richard II, he probably fought at the Battle of Otterburn with Henry "Hotspur" Percy in 1388. After Richard was deposed by Henry IV in 1399, de Umfraville loyally served the new Lancastrian regime, waging both offensive and defensive military operations against the Scots. Where necessary, he was also an effective diplomat, taking part in many embassies to Scotland and negotiating treaties. With the exception of Henry V's resumption of the Hundred Years' War in 1415—when de Umfraville travelled with the king to France, where he may have taken part in the Battle of Agincourt—all his military activity was on the Scottish border. He was famed for his martial prowess; one contemporary chronicler, John Hardyng, who was in de Umfraville's service, lauded him as the perfect knight. De Umfraville's successes in the north attracted praise and reward from the king. One campaign deep into Scottish territory resulted in his destroying Peebles and its market; he brought back so much booty that he was popularly nicknamed "Robin Mendmarket".
De Umfraville married but did not have children. His nephew and closest relative, Gilbert, predeceased him, perishing at the Battle of Baugé in 1421. He remained in royal service almost to the last months of his life, but this service was of uncertain financial profitability. Most of his northern lands would have been prone to frequent ravaging by marauding armies, so his Midlands estates may have been his main source of income. He carried out his last mission to Scotland in March 1436 and died early the next year.