Girolamo Riario (1443 – 14 April 1488) was Lord of Imola and Forlì in the 15th century.
Born in Savona, Riario was the son of Paolo Riario and Bianca della Rovere. He was a nephew of Pope Sixtus IV, who granted him the seignory of Imola, as a dowry for his marriage with Caterina Sforza (daughter of Galeazzo Maria Sforza, Duke of Milan) in 1473.
Four years later, just after the marriage had been celebrated, Girolamo took control of Forlì, ousting the Ordelaffi.
In 1478 he was one of the plotters behind the Pazzi conspiracy, a plot to assassinate two prominent members of the Medici family in Florence. In addition to conspiring, he was an intended beneficiary, once Lorenzo and Giuliano de' Medici had been killed. In 1484, after the death of Sixtus IV, Caterina briefly occupied Castel Sant'Angelo in Rome on his behalf. Girolamo was Captain General of the Church.
Riario promoted several further plots against the Medici, but they all failed. In 1488 he was the last of the main Pazzi conspirators left alive, and was himself assassinated in a conspiracy led by two members of the Orsi family from Forlì, supposedly over a financial dispute. On 14 April, Checco and Ludovico Orsi entered the government palace, and one of them attacked Riario with a sword. Despite the presence of the Count's guards, a total of nine assassins slashed Riario to death, eventually flinging his corpse into a local piazza, where a crowd gathered in support of the assassins. The assassins then proceeded to loot the palace.
Although assassinations were not altogether uncommon in Renaissance Florence, they still had repercussions. Despite writing to Lorenzo de' Medici, who no doubt approved of the result of the assassination, they received no written support by the Medici family. Support, both military and popular, eventually sided with Riario's widow, and the Orsi brothers fled, taking what they could with them. Their remaining assets and family were soon destroyed by angry mobs.
Riario's body had been recovered from the piazza by a local friar, and once Riario's widow proved vindicated, she had the body cleaned up and laid in state for three days in the church of San Francesco.
Girolamo had six sons, Ottaviano, who officially inherited the lordship of Imola, Cesare, Giovanni Livio, Galeazzo, Francesco, and a daughter, Bianca by his wife, Caterina, and lastly an illegitimate son by another woman, named Scipio.
In the 2009 video game Assassin's Creed II, the Orsi brothers were actually hired by Caterina Sforza, only to later turn on her and attempt to kidnap Ottaviano and Bianca.
| Preceded by Taddeo Manfredi |
Lord of Imola 1474–1488 |
Succeeded by Caterina Sforza |
| Preceded by Francesco V Ordelaffi |
Lord of Forlì 1480–1488 |