1565–1566 conclave

The 1565–66 papal conclave was convened on the death of Pope Pius IV and ended in the election of Pope Pius V.

Background

Cardinal Vitellozzo Vitelli was Camerlengo; Cardinal Francesco Pisani, the most senior of the cardinals was Dean of the Sacred College. The conclave was made up of several small groups aligned either by family relations, such as those who favored Francesco Gonzaga; and by locale, such as the Florentines. A separate division lay between some of the younger cardinals eager to press the reforms of the Council of Trent, and their senior colleagues whose views of reform leaned towards the Inquisition, which use appeared sometimes to border on the political.
The various factions presented a difficulty for anyone trying to put together a two-thirds majority. Cardinal Farnese had the largest number of commitments, but not the thirty-five needed to elect. Cardinal Borromeo advised Farnese that while he couldn't agree to support him as a candidate, he was willing to work with him to select someone agreeable. Farnese suggested four names, including that of Antonio Ghislieri. Ghislieri was also acceptable to the Spanish. Within two hours, they had sufficient votes to elect Ghislieri.

Ippolito II d'Este and Guido Luca Ferrero left the conclave because of illness; Francesco Gonzaga died during the conclave on 6 January.