Antipope John XXIII

Antipope John XXIII
Miniature from the Chronicle of the Council of Constance by Ulrich of Richenthal
Elected	17 May 1410
Papacy began	25 May 1410
Papacy ended	29 May 1415
Predecessor	Roman claimant: Gregory XII Antipapal claimant: Pisan Alexander V Avignonian Benedict XIII
Successor	Roman claimant: Gregory XII Antipapal claimant: Avignonian Benedict XIII Florentine Felix V
Opposed to	Roman claimant: Pope Gregory XII Antipapal (Avignon) claimant: Antipope Benedict XIII
Orders
Ordination	24 May 1410 by Jean-Allarmet de Brogny
Consecration	25 May 1410 by Jean-Allarmet de Brogny
Created cardinal	27 February 1402 by Pope Boniface IX
Rank	Cardinal-Deacon
Personal details
Born	Baldassarre Cossa Procida, Kingdom of Naples
Died	1419 Florence, Republic of Florence
Buried	Tomb of Antipope John XXIII
Alma mater	University of Bologna
Coat of arms
Other popes and antipopes named John

Baldassarre Cossa (died 22 December 1419) was Pisan antipope as John XXIII (1410–1415) during the Western Schism. The Catholic Church today regards him as an antipope in opposition to Pope Gregory XII, whom it recognizes as the rightful successor of Saint Peter. John XXIII was also an opponent of Benedict XIII, who was recognized by the French clergy and monarchy as the legitimate pope.

Historically, the Annuario Pontificio recognized John XXIII the legitimate successor of Saint Peter.^[1] However, the Western Schism was reinterpreted when Pope John XXIII chose to reuse the ordinal XXIII, which is now reflected in modern editions of the Annuario Pontificio.^[2] John XXIII is now considered to be an antipope and Gregory XII's reign is recognized to have extended until 1415.

Cossa was born in the Kingdom of Naples. In 1403, he served as a papal legate in Romagna. He participated in the Council of Pisa in 1408, which sought to end the Western Schism with the election of a third alternative pope. In 1410, he succeeded Antipope Alexander V, taking the name John XXIII. At the instigation of King Sigismund of Germany, Pope John called the Council of Constance of 1413, which deposed John XXIII and Benedict XIII, accepted Gregory XII's resignation, and elected Pope Martin V to replace them, thus ending the schism. John XXIII was tried for various crimes, though later accounts question the veracity of those accusations. Towards the end of his life Cossa restored his relationship with the Church and was made Cardinal Bishop of Frascati by Pope Martin V.