Pope John XX

Some 11th century historians believed that there had been a pope named John between antipope Pope Boniface VII and the actual Pope John XV[?]. Thus the series of Pope John XV[?] to Pope John XIX was mistakenly numbered John XVI to XX. These popes have been renumbered as John XV to XIX; however Pope John XXI and Pope John XXII were numbered based on the confusion of having twenty Pope Johns before them. Hence Pope John XX doesn't exist, having been skipped over in the enumeration of popes. As the enumeration is now firmly established, it is unlikely that any attempt at rectification will be made.

See also: List of Popes