Pope Gregory XII:
Pope Gregory XII resigned the papacy in 1415 to put an end to the Western Schism, which had divided the church for 40 years.
Born Angelo Corrario, the Italian cardinal was unanimously elected pope in 1406, in part due to his earnest desire to end the split within the church that had resulted in two men — one in Rome and one in Avignon, France — claiming to be the true pope since 1377. He took the name Gregory XII and promised the Council of Cardinals that he would happily resign his office, provided that his rival pope in France would do the same, so that a new leader could be elected and the church could be united. The newly appointed Gregory XII contacted the other pope, Benedict XIII, and offered to meet so that they could negotiate a settlement that would pacify both factions of the church.
Thus began six years of political maneuvering and holy power struggles. Although Gregory XII seemingly took St. Peter's Chair with the best intentions, he wavered when his rival pope showed no intentions to meet or resolve the Schism. Frustrated by inaction and the growing damage to the office of the papacy, in 1409, both groups of cardinals abandoned their respective popes and began to negotiate a settlement. Unfortunately, this only resulted in the election of a THIRD pope, known as the "antipope," Alexander V.
Catholic leaders across Europe called for another ecumenical council to end the confusion, and in 1414, cardinals, bishops, archbishops, abbots (heads of monasteries), and doctors of divinity met in Constance, Germany, to end the Schism once and for all. Since canon law dictates that only a pope can call a council, in 1415, Pope Gregory XII sent representatives to Germany, granting them the power to open the Council of Constance and present his resignation to the assembly.
The Council accepted Gregory XII's resignation and appointed him Bishop of Porto and perpetual legate at Ancona (making him the most powerful person in the church after the pope). The cardinals delayed electing a new pope so that they could resolve doctrinal and political problems that had plagued the church for years.
Gregory XII died in Ancona, Italy, on Oct. 18, 1417. The Council of Constance (which was still in session) elected the new pope, Martin V, in November 1417, and the Catholic Church was once again united.