The gens Petronia was a plebeian family at ancient Rome. This gens claimed an ancient lineage, as a Petronius Sabinus is mentioned in the time of Lucius Tarquinius Superbus, the last of the Roman kings, but few Petronii are mentioned in the time of the Republic. They are frequently encountered under the Empire, holding numerous consulships, and eventually obtaining the Empire itself during the brief reign of Petronius Maximus in AD 455.

Petronius Maximus was Roman emperor of the West for two and a half months in 455. A wealthy senator and a prominent aristocrat, he was instrumental in the murders of the Western Roman magister militum, Aëtius, and the Western Roman emperor, Valentinian III.