William le Scrope, 1st Earl of Wiltshire, King of Mann KG (1350–1399) was a close supporter of King Richard II of England. He was a second son of Richard le Scrope, 1st Baron Scrope of Bolton.
He was a soldier-adventurer in Lithuania,Italy and France, where he served with John of Gaunt. Gaunt made him seneschal of Aquitaine in 1383. He was made vice-chamberlain of the household of King Richard II in 1393 and granted the castle and manor of Marlborough in Wiltshire. In the same year his father purchased for him the Isle of Man from the earl of Salisbury, giving him the nominal title Dominus de Man or King of Mann. In 1394 he became a Knight of the Garter.
He was created Earl of Wiltshire in 1397 and became Lord High Treasurer in 1398. He became effective head of the government in Richard's absence. He benefitted from the confiscated estates of Thomas de Beauchamp, 12th Earl of Warwick, who was kept for a time under his care in the Isle of Man, and of John of Gaunt; he also accumulated control of a number of strategic castles. He was left 2,000 marks in King Richard's will in April 1399.
He had been closely involved in Richard's second marriage to the 6-year-old Isabella of Valois in 1396 and was made Isabella's guardian at Wallingford Castle, of which he was castellan, when the King went to Ireland in 1399.