William de Longchamp[a] (died 1197) was a medieval Lord Chancellor, Chief Justiciar, and Bishop of Ely in England.

When Richard became king in 1189, Longchamp paid £3,000 for the office of Chancellor and was soon named to the Diocese, or bishopric, of Ely and appointed legate by the pope.

He aroused a great deal of hostility among his contemporaries during his career, but he retained Richard's trust and was employed by the king until the bishop's death in 1197.

[9] Longchamp entered public life at the close of Henry II's reign, as an official for the King's illegitimate son Geoffrey.

[12] Historians' opinions are divided whether Richard explicitly made Longchamp superior to Puiset at this time, or if in theory the two were supposed to co-equal in their respective spheres.

[21] Longchamp granted the citizens of London the right to elect their own sheriffs, and to collect and remit their monetary levy of £300 directly to the Exchequer, the treasury of England.

[22] On Longchamp's visits to his diocese he was accompanied by a large train of retainers and animals, which became notorious throughout the country as a sign of his extravagance.

Also in 1190, he sent an army against Rhys ap Gruffydd, a Welsh prince who was attempting to throw off the control of the marcher lords that surrounded Wales.

[25] The leading nobles complained that Longchamp marginalised the other officials Richard had appointed to serve with him and that he brought in foreigners to fill offices.

[28] News of the dispute reached Richard, who sent Walter de Coutances, the Archbishop of Rouen, to England in late spring 1191, with orders to negotiate a peace between John and Longchamp.

[27] One of the leaders of the campaign against Longchamp was Hugh Nonant, the Bishop of Coventry, and he along with other magnates, including Geoffrey, who had been released, convened a trial on 5 October 1191 at Loddon Bridge near London.

Hugh Nonant wrote that Longchamp attempted on one occasion to hide dressed as a prostitute, which led to him being assaulted by a fisherman who mistook him for a whore.

[3] Longchamp went to the court of Henry VI, the Holy Roman Emperor, who was holding King Richard captive at Trifels.

[3] Richard continued to use Longchamp in diplomacy[34] — although it was Geoffrey who arranged a truce with King Philip in 1194[34] — as well as retaining the bishop as chancellor, but the main power in England was now Hubert Walter.

[36] Longchamp died in January 1197,[16] at Poitiers,[35] while on a diplomatic mission to Rome for Richard,[37] and was buried at the abbey of Le Pin.

[12] He was supported by others among his contemporaries, including Pope Clement III, who, when he appointed Longchamp legate, wrote that he did so at the urging of the English bishops.

[40] Historian John Gillingham wrote that Longchamp's "record of his life in politics and administration was a good one, spoiled only by his failure in 1191".

[12] Two writers have seen, in the assembly that met to try Longchamp in 1191, a precursor to the gathering at Runnymede in 1215 that drew up Magna Carta, as it was one of the earliest examples of the nobles of the realm coming together to force the government to rule with their advice.

[8] His brother Robert, a cleric, also benefitted, becoming prior of the Ely cathedral chapter and later abbot of St Mary's Abbey, York.

[43] Richard Barre, a medieval writer and judge, dedicated his work Compendium de veteris et novo testamento to Longchamp.

[45] One of Longchamp's probable innovations as chancellor was the replacement of the first person singular previously used in documents drafted in the king's name with the majestic plural or "royal we".