Robert Hallam (died September 4, 1417), was an English churchman, Bishop of Salisbury and English representative at the Council of Constance. He was Chancellor of the University of Oxford from 1403 to 1405.

Hallam had been educated at Oxford. On leaving the chancellorship, he was nominated by the pope as Archbishop of York, but the appointment was vetoed by King Henry IV. However, in 1407 he was consecrated by Pope Gregory XII at Siena as Bishop of Salisbury. At the Council of Pisa in 1409 he was one of the English representatives. On June 6, 1411 Antipope John XXIII (Baldassare Cardinal Cossa) purported to make Hallam a cardinal, but this title was not recognized.

At the Council of Constance, in November 1414, Hallam was the chief English envoy. There he took a prominent position, as an advocate of Church reform and of the superiority of the council to the pope. He played a leading part in the discussions leading to the deposition of John XXIII on May 29, 1415, but was less concerned with the trials of Jan Hus and Jerome of Prague. Sigismund, Holy Roman Emperor, through whose influence the council had been assembled, was absent during the whole of 1416 on a diplomatic mission in France and England; but when he returned to Constance in January 1417, as the open ally of the English king, Hallam as Henry V's trusted representative obtained increased importance, and contrived to emphasize English prestige by delivering the address of welcome to Sigismund. Afterwards, under Henry's direction, he supported the emperor in trying to secure a reform of the Church, before the council proceeded to the election of a new pope. This matter was still undecided when Hallam died suddenly. After his death the cardinals were able to secure the immediate election of a new pope, (Martin V, elected on November 11): It has been said that the abandonment of the reformers by the English was due entirely to Hallam's death; but it is more likely that Henry V, foreseeing the possible need for a change of front, had given Hallam discretionary powers which the bishop's successors used. Hallam himself had the confidence of Sigismund and was generally respected for his straightforward independence. He was buried in the cathedral at Constance, where his tomb near the high altar is marked by a brass of English workmanship.

This entry is updated from the 1911 Encyclopedia Britannica.