[1] Such a year generally occurs when a newly elected pope dies or resigns very early into his papacy.
This results in the Catholic Church being led by three different popes during the same calendar year.
The most recent instance of a year of three popes occurred in 1978.
The three popes involved were:[2] There have been thirteen instances in which exactly three popes have held office in a given calendar year.
Years in which the Roman Catholic Church was led by three different popes include: There was also a year in which the Roman Catholic Church was led by four popes, called the Year of Four Popes: