Northumberland, Henry Percy, 1st earl of, 1342–1408, English nobleman. He fought in France in the Hundred Years War, became warden of the Scottish Marches, and was a supporter of John Wyclif. Created earl of Northumberland by Richard II in 1377, he and his son Sir Henry Percy (Hotspur) were engaged in constant warfare with the Scots. He was a leading supporter of Henry of Lancaster (Henry IV) in the usurpation of 1399, but with his brother, Thomas Percy, earl of Worcester, and Hotspur, Northumberland revolted against the king in 1403. He submitted after the death of his son at the battle of Shrewsbury in the same year. By 1405, however, he was plotting again with Owen Glendower and, after fleeing to Scotland and France, invaded (1408) England from the north with the expectation of recruiting followers. He was slain and his forces were defeated at Bramham Moor.