The 1591 papal conclave (27–29 October) was held after the death of Pope Gregory XIV on 16 October that year, after less than a year as pope.

The conclave lasted only three days and elected Pope Innocent IX.

Philip II of Spain's (r. 1556–1598) high-handed interference at the previous conclave was not forgotten: he had barred all but seven cardinals.

This time the Spanish party in the College of Cardinals did not go so far, but they still controlled a majority, and after a quick conclave they raised Facchinetti to the papal chair as Pope Innocent IX.

Facchinetti received 24 votes on 28 October but was not successful in that ballot to be elected as pope.