Marcus Petronius Mamertinus, possibly known as Sextus Petronius Mamertinus, was a Roman senator originally of the Equestrian order. He served as suffect consul in 150 as the colleague of . Edward Champlin has argued that Petronius Mamertinus is a kinsman of the orator Fronto, based on a letter Fronto wrote to Petronius, commending a young man to him, in which Fronto addresses Petronius as a member of "our familia". Champlin writes, "There can be no doubt that here, as elsewhere, familia means precisely family to Fronto." Anthony Birley notes this supports his earlier argument that Petronius had an African origin, and further argues that his postulated wife, Septimia, was a cousin of the future emperor Septimius Severus. On the other hand, Géza Alföldy suggested Petronius had an Italian bac