Orsini

The Orsini of Monterotondo were a Roman baronial branch of the Orsini family, founded by Rinaldo, a son of Matteo Rosso the Great, after the family bought Monterotondo from the Capocci in the twelfth century. On the Via Salaria north of Rome, the town was a strategic stronghold in the city's defense.

Rinaldo's son Napoleone became a cardinal in 1288 and remained a leading figure of the Curia until his death at Avignon in 1342. Orso Orsini was killed fighting for the king of Naples at the Battle of Zagonara in 1424; his son Giacomo served the Papal States, Naples and Florence in turn.

Giacomo's daughter Clarice married Lorenzo de' Medici of Florence in 1469. Cardinal Giovanni Battista Orsini was strangled in 1503 after the failed plot against Cesare Borgia. The branch declined from the late sixteenth century and its last heirs sold Monterotondo to the Barberini in 1641.