The Council of Constance, called by Pope John XXIII, the Pisan pope, with the support of Emperor Sigismund, held from 1414 to 1418 in Constance, was an ecumenical council of the Christian Church. Its main purpose was to end the Papal schism which had resulted from the Avignon Papacy, or as it is sometimes known, the "Babylonian Captivity of the Church."

At the time the council was called, there were three popes, all of whom claimed legitimacy. A few years earlier, in one of the first blows of the Conciliarist movement, the bishops at the Council of Pisa had deposed both of the two claimant popes and elected a third pope, claiming that in such a situation, a council of bishops had greater authority than just one bishop, even if he be the bishop of Rome. This had only furthered the schism.

With the support of the Sigismund, Holy Roman Emperor, the Council of Constance recommended that all three popes abdicate, and that another be chosen. In part because of the constant presence of the emperor, other rulers demanded that they have a say in who would be pope. Much of the Council's time was therefore occupied with trying to placate secular rulers rather than in actual reform of the Church and its hierarchy.

A second goal of the council was to continue the reforms begun at the Council of Pisa. These reforms were largely directed against John Wyclif, Jan Hus, and their followers. Jan Hus was condemned by council and burned at the stake on July 6, 1415.

The council also attempted to direct ecclesiastical reforms.

It was later declared that a council of Bishops has no greater authority than the Pope.

During the council there were also political topics discussed, such as the accusation by the Teutonic_Knights that Poland was defending pagans. Pawel Wlodkowic, rector of the Jagiellonian University in Cracow, Poland, presented there the theory that all nations, including pagan ones, have the right to self-govern and to live in peace and possess their land which is one of the earliest ideas of international law.