Western Schism
The Western Schism or Papal Schism was a split within the Catholic Church in 1378. Lacking any real theological or doctrinal underpinnings, being rather driven by politics, it was resolved after 40 years by the Council of Constance. It is occasionally called the Great Schism, though this term is more often applied to the East-West Schism of 1054.The schism in the Western church resulted from the return of the Papacy from Avignon to Rome by Pope Gregory XI in 1378, ending the Avignon Papacy.
After Gregory XI died, the Romans rioted to ensure an Italian was elected; the cardinals, fearing the crowds, elected an Italian, Pope Urban VI in 1378; but in the same year the majority of them removed themselves to Fondi, and elected a rival Pope from there, Pope Clement VII. Later a council at Pisa was held in 1409 to try to solve the dispute, but it only resulted in the election of a third Pope, Pope Alexander V by the council, soon to be followed by Pope John XXIII.
Finally, the Council of Constance in 1417 deposed John XXIII and the Avignon Pope Benedict XIII, received the resignation of the Roman Pope Gregory XII, and elected Pope Martin V, thereby ending the schism.
From this time forward in the Catholic church it was decreed explicitly that no Council had power over the Popes, and there is no way to undo a Papal election by anyone but the pope.
The alternate papal claimants have become known in history as antipopes.
The Great Schism of the Western Church occupied the energies of Jean Gerson, one of the great theologians of the age.