The Pazzi Conspiracy was a conspiracy including many members of the Pazzi family of Florence and the Archbishop of Pisa, supported by Pope Sixtus IV, whose object was to remove the Medici family from power in Florence.

On April 26, 1478, members of the conspiracy attacked the Medici brothers and co-leaders Lorenzo and Giuliano in the Cathedral of Santa Maria del Fiore (site of Bruneschelli's famous Duomo), killing Giuliano. Other members tried to capture the Gonfaloniere and Signoria; when this was thwarted when those conspirators were trapped in a room whose doors had a hidden latch, the coup failed.

Lorenzo's allies vowed revenge, and had the Archbishop and several other co-conspirators (including one of the Pazzi family members who had killed Giuliano, Francesco de' Pazzi) hanged from the windows of the Palazzo della Signoria. 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 also killed.

Lorenzo did manage to save the nephew of Sixtus IV, Cardinal Raffaele Riario, who was almost certainly an innocent dupe of the plotters, as well as two relatives of plotters.

Of the conspirators who had managed to escape the immediate aftermath, only one is known to have survived; the rest were tracked down and suffered brutal deaths. The Pazzi family were totally supressed; all places named after them were renamed; their insignia destroyed wherever they were found in the city, and similar measures.