Quote Originally Posted by JohnQPublic View Post
Pope Gregory XII (1406–1415) resigned in 1415 in order to end the Western Schism, which had reached the point where there were three claimants to the Papal throne: Roman Pope Gregory XII, Avignon Antipope Benedict XIII, and Pisan Antipope John XXIII. Before resigning he formally convened the already existing Council of Constance and authorized it to elect his successor.


I was afraid of this. This was not a normal papal resignation. I'm not sure there ever has been such.
http://en.m.wikipedia.org/wiki/Pope_Celestine_V

Although it was often said that Celestine was the only pope to resign voluntarily (prior to Benedict XVI doing so in 2013), in fact, other popes have similarly abdicated of their own will. These are John XVIII in 1009 and Benedict IX in May 1045 (although he regretted it and was soon back). There was also Gregory XII in 1415 who agreed to quit at the request of the Council of Constance. Benedict XVI announced his resignation in February 2013.