The Pazzi conspiracy was a plot by members of the Pazzi family and others to displace the de' Medici family as rulers of Renaissance Florence. On 26 April 1478 there was an attempt to assassinate Lorenzo de' Medici and his brother Giuliano de' Medici. Lorenzo was wounded but survived; Giuliano was killed. The failure of the plot served to strengthen the position of the de' Medici. The Pazzi were banished from Florence.
The Pazzi family were not the only instigators of the plot. The Salviati, Papal bankers in Florence, were at the centre of the conspiracy. Pope Sixtus IV was an enemy of the Medici. He had purchased from Milan the lordship of Imola, a stronghold on the border between Papal and Tuscan territory that Lorenzo de' Medici wanted for Florence. The purchase was financed by the Pazzi bank, even though Francesco de' Pazzi had promised Lorenzo they would not aid the Pope. As a reward, Sixtus IV granted the Pazzi monopoly at the alum mines at Tolfa — alum being an essential mordant in dyeing in the textile trade that was central to the Florentine economy — and he assigned to the Pazzi bank lucrative rights to manage Papal revenues. Sixtus IV appointed his nephew, Girolamo Riario, as the new governor of Imola, and Francesco Salviati as archbishop of Pisa, a city that was a former commercial rival but now subject to Florence. Lorenzo had refused to permit Salviati to enter Pisa because of the challenge such an ecclesiastical position offered to his own government in Florence.
Girolamo Riario, Francesco Salviati and Francesco de' Pazzi put together a plan to assassinate Lorenzo and Giuliano de' Medici. Pope Sixtus was approached for his support. He made a very carefully worded statement in which he said that in the terms of his holy office he was unable to sanction killing. He made it clear that it would be of great benefit to the papacy to have the Medici removed from their position of power in Florence, and that he would deal kindly with anyone who did this. He instructed the men to do what they deemed necessary to achieve this aim, and said that he would give them whatever support he could. In 2004, an encrypted letter in the archives of the Ubaldini family was discovered by historian Marcello Simonetta and decoded. It revealed that Federico da Montefeltro, Duke of Urbino, a renowned humanist and condottiere for the Papacy, was deeply embroiled in the conspiracy and had committed himself to position 600 troops outside Florence, waiting for the moment.
On Sunday, 26 April 1478, during High Mass at the Duomo before a crowd of 10,000, the Medici brothers were assaulted. Giuliano de' Medici was stabbed 19 times by Bernardo Bandi and Francesco de' Pazzi. As he bled to death on the cathedral floor, his brother Lorenzo escaped with serious, but non life-threatening wounds. Lorenzo was locked safely in the sacristy by Agnolo Poliziano. A coordinated attempt to capture the Gonfaloniere and Signoria was thwarted when the archbishop and head of the Salviati clan were trapped in a room whose doors had a hidden latch. The coup d'état had failed, and the enraged Florentines seized and killed the conspirators. Jacopo de' Pazzi was tossed from a window. To finish him off, the mob dragged him naked through the streets, then threw him into the Arno River. The Pazzi family were stripped of their possessions in Florence, every vestige of their name effaced. Salviati was hanged on the walls of the Palazzo Vecchio. Although Lorenzo appealed to the crowd not to exact summary justice, many of the conspirators, as well as many people accused of being conspirators, were killed. Lorenzo did manage to save the nephew of Sixtus IV, Cardinal Raffaele Riario, who was almost certainly an innocent dupe of the conspirators, as well as two relatives of the conspirators. The main conspirators were hunted down throughout Italy and the fortunes of the various Pazzi companies across Europe were despoiled. The Pazzi coat of arms and all references to the family's name were banned.
In the aftermath of the "Pazzi" conspiracy, Pope Sixtus IV placed Florence under interdict, forbidding Mass and communion, for the execution of the Salviati archbishop. Sixtus enlisted the traditional Papal military arm, the King of Naples, Ferdinand I, to attack Florence. With no help coming from Florence's traditional allies in Bologna and Milan, Lorenzo was faced with dire prospects and adopted an unorthodox course of action: he sailed to Naples and put himself in the hands of Don Ferrante (the king), in whose custody he remained for three months. Lorenzo's courage and charisma convinced Don Ferrante to support Lorenzo's attempts at brokering a peace and intercede, albeit ineffectually, with Sixtus IV. The events of the Pazzi conspiracy affected the developments of the Medici regime in two ways: they convinced the supporters of the Medici that a greater concentration of political power was desirable and they strengthened the hand of Lorenzo de' Medici who had demonstrated his keen ability in conducting the foreign affairs of the city. Emboldened, the Medicean party carried out new reforms.
In 1494, however, with the overthrow of Piero de' Medici, the Pazzi family, and many other political exiles, returned to Florence to participate in the popular government.
The conspirators, Francesco de' Pazzi, Bernardo di Bandino Baroncelli, Archbishop Salviati, Renato de' Pazzi, Messer Jacopo de' Pazzi, Antonio Maffei and Stefano de Bagnone, were depicted in a painting by Sandro Botticelli on either a wall of the Bargello or a wall of the Dogana, part of the government-complex. The Pope Alexander VI pressured Florence to remove these lifelike pictures, and they were eventually destroyed in 1494 after the overthrow of the Medici.
Vittorio Alfieri's play La congiura de' Pazzi (first performance 1787, first published 1789) is a version of the story of the conspiracy, as is the opera I Medici by Ruggero Leoncavallo.
The conspiracy was used as the major climatic cliffhanger in the historical fantasy drama series Da Vinci's Demons, with the assassination attempts occurring in the season 1 finale, with the body and aftermath of the conspiracy taking place in the first two episodes of season 2. This version of events did stray somewhat from history, in terms of participants, but was careful not to step outside as true a representation of events as possible.
- Hugh Ross-Williamson, p. 165
- Marcello Simonetta, The Montefeltro Conspiracy: A Renaissance Mystery Decoded, Doubleday (2008) ISBN 0385524684
- Lauro Martines (2003) April Blood: Florence and the Plot Against the Medici. Oxford: Oxford University Press, ISBN 9780195176094. pp. 187-196. Tobias Daniels: La congiura dei Pazzi: i documenti del conflitto fra Lorenzo de’ Medici e Sisto IV. Le bolle di scomunica, la “Florentina Synodus”, e la “Dissentio” insorta tra la Santità del Papa e i Fiorentini. Edizione critica e commento, Edifir, Florence 2013, ISBN 978-88-7970-649-0
- Nicolai Rubinstein (1997) The government of Florence under the Medici (1434-1494). Oxford: Oxford University Press. p. 223.
- Martines, 135.