He was born Francesco Della Rovere in Abisola, Italy. He joined the Franciscan order and his intellectual qualities were revealed while he was studying philosophy and theology at the University of Pavia. He went on to lecture at many eminent Italian universities. He was made Minister General of the Franciscan order in 1464. In 1467 he was made a Cardinal by Pope Paul II.
After his election temporal issues were his main concern. He was energetic in raising support for war against the Turks, although the resulting crusade was ineffective. Sixtus continued the arguing with Louis XI of France for insisting on royal consent to papal decrees. Like a number of Popes, Sixtus was guilty of nepotism, in his territoral aggrandizement of the Papal States one of his nephews - Cardinal Rafael Riario was a leader in the 1478 conspiracy and assassination to take Florence from the Medici. The pope followed the death of Giuliano de Medici with a interdict and two years' of war with Florence, he also encouraged the Venetians to attack Ferrara, which he wished to obtain for another nephew. The angered Italian princes allied to force Sixtus to make peace, an act which annoyed Sixtus immensely.
Sixtus was Pope when the Spanish Inquisition was instituted in Seville. He worked against it, but bowed to pressure from Ferdinand of Aragon, who threatened to withhold military support from his kingdom of Sicily. Sixtus issued the bull establishing the order in 1478. Nevertheless Sixtus was unhappy with the excesses of the Inquisition and took measures to suppress their abuses.
He supported the claim by Portugal to ownership of the newly discovered Americas by a bull in 1481.
The Sistine Chapel was sponsored by Sixtus as was the Sistine Bridge, he also had the San Vitale rebuilt in 1475 and boosted the Vatican Library. He had Regiomontanus attempt the first sactioned reorganization of the Julian calendar.
| Preceded by: Pope Paul II | List of popes | Succeeded by: Pope Innocent VIII |