Origins & Early Life

Baldassarre Cossa (died November 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.

Pivotal Works & Achievements

However, the Western Schism was reinterpreted in 1958 when Pope John XXIII chose to reuse the ordinal XXIII, which is now reflected in modern editions of the Annuario Pontificio. 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.

Enduring Legacy & Impact

In 1410, he succeeded Antipope Alexander V, taking the name John XXIII. At the instigation of King Sigismund of Germany, John XXIII called the Council of Constance of 1413, which deposed both John...

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