Mortimer, Edmund de, 3d earl of March and 1st earl of Ulster [key], 1351–81, English nobleman. He succeeded (1360) his father, Roger, 2d earl of March, married (1368) Philippa, daughter of Edward III's son Lionel, duke of Clarence, and on Lionel's death (1368) inherited his estates and the title of earl of Ulster. Later the house of York (see York, house of) traced part of its claim to the throne to this union. Mortimer held the office of marshal of England from 1369 to 1377 and supported the party that opposed John of Gaunt. After the accession of Richard II (1377) he was elected to the boy king's first council. In 1379 he was sent as lieutenant of Ireland to subdue Irish unrest. His daughter Elizabeth married Sir Henry Percy, known as Hotspur.
