Why the Roman Catholic Church has struggled to define its own list of popes.

History · Published 3 October 2026 Swipe more like this →

In short: An antipope is not merely a pretender, but a figure who successfully challenged a sitting pope, creating deep historical ambiguity. Because records are often biased or incomplete, the Church itself cannot definitively list every antipope, and some figures once labeled as rivals are now debated as legitimate successors to Saint Peter.

The definition of an antipope is deceptively simple: one who opposes a legitimately elected pope and achieves some material success in that pursuit. However, the reality is far more complex. Historians generally concede there were at least 37 antipopes between 217 and 1439, yet the lack of clear, contemporary records means that even those living through these schisms often could not identify the true pontiff.

Antipopes emerged from various conflicts, including doctrinal disputes, political exiles, and double elections arbitrated by secular rulers. A notable example is the Great Western Schism, which began in 1378. This crisis resulted in three simultaneous papal claimants based in Rome, Avignon, and Pisa. It was not until the election of Martin V on November 11, 1417, that the Church achieved unity, effectively ending the competing lines of authority.

The confusion extends to the very numbering of popes. Because some 11th-century historians mistakenly believed a pope existed between the antipope Boniface VII and John XV, subsequent popes were misnumbered. This error persists today; for instance, there is no Pope John XX. Furthermore, the Annuario Pontificio notes that for certain elections, such as those involving Leo VIII or Sylvester III, it is impossible to reconcile historical, theological, and canonical criteria to determine legitimacy, leading the Church to abandon strict sequential numbering in those instances.

While modern claimants exist, particularly within the Sedevacantist movement, they lack the mainstream influence of their medieval predecessors. Scholars like Magnus Lundberg prefer the term alternative popes for these figures, as the historical weight of the title antipope is reserved for those who once fundamentally threatened the unity of the Roman Catholic Church.

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