Pembroke, William Marshal, 1st earl of, d. 1219, English nobleman. He became (1170) a guardian of Prince Henry, eldest son of Henry II, and supported him in his abortive rebellion (1173–74) against his father. After the prince's death (1183), however, he went on crusade for the king. Upon the accession (1189) of Richard I, Marshal married Isabella, heiress of Richard de Clare, 2d earl of Pembroke, and took her titles, thereby becoming 1st earl of Pembroke in the Marshal line. During Richard I's absence from England, Marshal supported the king's brother John against William of Longchamp but helped thwart John's 1193 rebellion. Once John became king, however, the earl supported him and was one of his counselors at Runnymede. Elected regent for the young Henry III by the barons in 1216, Marshal successfully waged war against the invading Prince Louis (later Louis VIII) of France and by a firm policy toward recalcitrant barons secured a relatively stable kingdom.
See S. Painter, William Marshal (1933, repr. 1967).