The gens Petreia was a minor plebeian family at ancient Rome.
Members of this gens are first mentioned toward the end of the second century BC, and several were distinguished as soldiers, but none of them ever attained the consulship.
However, in this instance it seems more likely that Petreius is a patronymic surname, derived from the Oscan praenomen Petrus or Petro.
In inscriptions, Marcus, Gaius, Lucius, and Quintus are regularly found, while other names are hardly used.
Numerous cognomina appear in inscriptions, most of which are from imperial times, but none of them seem to represent distinct families.