The election of Petros Philargos as Pope Alexander V commenced during the Council of Pisa, an attempt to resolve the Western Schism that had plagued the Catholic Church since the election of Pope Urban VI in 1378. The church was divided between two popes: Gregory XII, who resided in Rome, and Benedict XIII, who governed from Avignon. The council convened to address the legitimacy of both papacies and aimed to re-establish a unified papal authority in the face of growing disillusionment among the faithful and political leaders alike. The delegates, consisting of cardinals, bishops, and representatives from various regions, sought to forge a consensus that could heal the rift within the Church.

On June 26, 1409, the assembly elected Petros Philargos, who took the name Alexander V, in one of the pivotal moments of this council. His election was largely aimed at providing a third option that could unite the factions, as many believed neither Gregory XII nor Benedict XIII was capable of restoring peace and legitimacy to the papacy. Despite the intentions behind his election, the situation only deepened the schism, as both Gregory XII and Benedict XIII refused to recognize Alexander V's authority, leading to a tripartite division of the papacy. This further complicated the ecclesiastical landscape and set the stage for prolonged conflicts within the Church.

The Council of Pisa did not ultimately succeed in resolving the conflict but instead intensified political and doctrinal disputes, impacting the authority of the papacy for years to come. Over the subsequent years, various efforts by emperors and ecclesiastical bodies to quell the unrest proved largely ineffective, resulting in continued fragmentation of Catholic authority throughout Europe. Alexander V's short papacy ended with his death in 1410, which left the schism unresolved and led to the subsequent election of Pope John XXIII, further complicating an already volatile situation.