The 1655 papal conclave was convened following the death of Pope Innocent X and ended with the election of Cardinal Fabio Chigi as Alexander VII.

The 1655 papal conclave was a notable event in the history of the Catholic Church, reflecting the political complexities of the time and resulting in a change of leadership.

[1][2] During Innocent's papacy, the Peace of Westphalia brought an end to the Thirty Years' War, the most significant secular event that occurred during his reign.

There were eighteen cardinals loyal to Spain in the conclave, and while the French had less loyalty, Urban VIII's nephew Francesco Barberini was a member of their faction.

[3] Giulio Cesare Sacchetti, who had been considered the most likely to become pope in 1644, was the strongest candidate again, but some cardinals did not vote for him because he had been vetoed in the previous conclave by the Spanish.

[6] In mid-February, Sacchetti, recognizing that his own candidacy was lost, contacted Mazarin and requested that the French cardinals move their support to Fabio Chigi.

On the first scrutiny on 7 April 1655, twenty written ballots were cast for Chigi, before the other electors acclaimed him pope after a conclave lasting eighty days.