Today in Christian History – March 25

1409 – The Council of Pisa meets to depose rival popes and elect a third, who will call himself Alexander V. Since neither of the other two will accept the council’s authority, there will now be three popes instead of two.

http://www.christianhistoryinstitute.org/today/3/25

The Council of Pisa was an unrecognized ecumenical council of the Catholic Church held in 1409 that attempted to end the Western Schism by deposing Benedict XIII (Avignon) and Gregory XII (Rome). Instead of ending the Western Schism, the Council elected a third papal claimant, Alexander V, who would be succeeded by John XXIII.

http://en.wikipedia.org/wiki/Council_of_Pisa