Pope Sixtus IV (1414 – 1484), born Francesco della Rovere, was Pope from 1471 to 1484. He was famed for his support of and involvement in the Pazzi conspiracy. He was also responsible for ushering the Renaissance era into Rome. His nephew, Giuliano della Rovere, would become Pope Julius II.
Shortly after he was elected Pope in 1471, he was visited by Giovanni Auditore on behalf of Lorenzo de' Medici - de facto ruler of Florence. Giovanni sought to secure the new Pope's support of the Medici bank, and after negotiating, was successful.
By 1476, Sixtus was heavily influenced, though apparently wary, of Cardinal Rodrigo Borgia, who was also the Grand Master of the Templar Order. Around December 27, 1476, he was visited in the Vatican by Cardinal Borgia, who requested support for the Pazzi family in their planned takeover of Florence. Due to his dislike of Lorenzo de' Medici – who he said did not share the Vatican's view – Sixtus lent his moral support to the operation, but added that he could not consent to murder, as it was not his place, and gave his military support on the condition that no one was killed.
In 1478, Sixtus authorized the establishment of the Spanish Inquisition at the request of Ferdinand II of Aragon and Isabella I of Castile, the King and Queen of Spain, permitting them to appoint priests as inquisitors.
Sixtus died on the 12th August 1484. Tradition holds he died because of a stroke he suffered after he read the terms of the Treaty of Bagnolo, hence his ally Ercole I d'Este, Duke of Ferrara, ceded Rovigo to Giovanni Mocenigo, Doge of Venice.
- Historically, Pope Sixtus IV gave his support to the Pazzi bank instead, despite giving his word that he would not to Lorenzo de' Medici.