| Month: | September |
| Year: | 1590 |
| Dates: | 7–15 September 1590[1] |
| Location: | Apostolic Palace, Papal States |
| Dean: | Giovanni Antonio Serbelloni |
| Subdean: | Alfonso Gesualdo |
| Camerlengo: | Enrico Caetani |
| Protopriest: | Mark Sittich von Hohenems Altemps |
| Protodeacon: | Andreas von Österreich |
| Pope Elected: | Giovanni Battista Castagna |
| Nametaken: | Urban VII |
| Prevconclave Year: | 1585 |
| Prevconclave Link: | 1585 papal conclave |
| Nextconclave Year: | October–December 1590 |
| Nextconclave Link: | October–December 1590 papal conclave |
The September 1590 papal conclave, attended by 54 cardinals, elected Cardinal Giovanni Battista Castagna as Pope Urban VII.[2]
The conclave lasted a week, and was heavily swayed by the influence of the twenty-two Spanish cardinals.[3] [4] Castagna, who had been favored by Sixtus V as a successor and was on the list of candidates whom Philip II of Spain had approved, was a favorite from the beginning,[5] although a significant opposing faction supported Marco Antonio Colonna.[6] Castagna's poor health, which would ultimately kill him after a papacy of only thirteen days, made him a more palatable candidate to cardinals who were outraged at Philip's attempts to sway the election.
Contemporary newspapers reported that a disagreement between Cardinals Ascanio Colonna and Francesco Sforza di Santa Fiora during the conclave nearly became violent.[7]