Giulio Orsini (died 1517) was an Italian condottiero. He was a member of the Orsini family. In the 1480s he fought alongside his brother Paolo against the rival Colonna in the Lazio. In 1494 he tried in vain to defend Rome against the troops of King Charles VIII of France. In the early 16th century, he took part in Cesare Borgia's conquest of Romagna: he was one of the few Borgia's captains who didn't plot against him (1502), but this did not prevent Pope Alexander VI to have him besieged in Ceri in the early 1503. Orsini surrendered but returned to Rome after Alexander's death.