He was the oldest son of Girolamo Riario, a nephew of Pope Sixtus IV who had obtained possessions in Italy thanks to the pontiff's patronage, and Caterina Sforza.

[2] After his father's murder, he was created lord of Imola and Forlì in July 1488 by Pope Innocent VIII, under the regency of his mother.

Ottaviano's friends plotted to use the episode as an excuse to "liberate" the city from the rule of Giacomo Feo by assassinating him.

Pope Alexander VI sent his son Cesare Borgia to capture Imola and Forlì, claiming that dues had not been paid.

[4] After Alexander's death Ottaviano made several attempts to recapture his territories, but was unable to muster sufficient forces to achieve his goal.