William Longchamp, (died Jan. 31, 1197, Poitiers, France), ecclesiastical statesman who governed England in 1190–91, while King Richard I (reigned 1189–99) was away from the kingdom during the Third Crusade.
Of Norman origin, Longchamp was made chancellor of England and bishop of Ely when Richard ascended the throne. After Richard’s departure on crusade, he became joint justiciar with Hugh de Puiset, bishop of Durham (March 1190). Longchamp soon drove Hugh from office, and in June 1190 he was appointed papal legate by Pope Clement III. Although he was able and completely loyal to Richard, Longchamp’s overbearing manner and anti-English prejudices earned him the hostility of the English people. Hoping to profit by this situation, Richard’s brother John (later King John, 1199–1216) rebelled and forced Longchamp to flee to France. Early in 1193 Longchamp visited Richard, who was being held prisoner in Germany, and arranged for the king to be ransomed. John’s rebellion collapsed upon Richard’s return to England (March 1194). Richard retained Longchamp as chancellor and employed him on diplomatic missions.