Gaius Calpetanus Rantius Quirinalis Valerius Festus was a Roman senator, general, and amicus to each of the Flavian emperors. He proved his value to the Flavians when, as legatus legionis, or commander, of Legio III Augusta stationed in Africa, he assassinated the proconsul, who favored a rival of Vespasian during the Year of Four Emperors. He maintained his loyalty through the reigns of his sons Titus and Domitian, but fell out of favor during the latter's reign and was forced to commit suicide. Tacitus describes him in AD 70 as "a young man of extravagant habits and immoderate ambition."