The gens Flavia was a plebeian family at ancient Rome. Its members are first mentioned during the last three centuries of the Republic. The first of the Flavii to achieve prominence was Marcus Flavius, tribune of the plebs in 327 and 323 BC; however, no Flavius attained the consulship until Gaius Flavius Fimbria in 104 BC. The gens became illustrious during the first century AD, when the family of the Flavii Sabini claimed the imperial dignity.
Under the Empire, the number of persons bearing this nomen becomes very large, perhaps due to the great number of freedmen under the Flavian dynasty of emperors. It was a common practice for freedmen to assume the nomina of their patrons, and so countless persons who obtained the Roman franchise under the Flavian emperors adopted the name Flavius, which was then handed down to their descendants.
During the later period of the Empire, the name Flavius frequently descended from one emperor to another, beginning with Constantius, the father of Constantine the Great. The name became so ubiquitous that it was sometimes treated as a praenomen, to the extent of being regularly abbreviated Fl., and it is even described as a praenomen in some sources, although it was never truly used as a personal name. The last emperor to take the name was eastern emperor Constantine IV, during the seventh century.
After the name fell into disuse among the Byzantine emperors, it was used as a title of legitimacy among the barbarian rulers of former Roman provinces, such as Spain, where the Visigoths and their Spanish successors used the title "Emperor of All Spain", and the kings of the barbarian successor kingdoms of Italy, such as the Ostrogoths and the Lombards also used it, with a special meaning as the "protector" of the Italian peoples under Lombard rule.
The vast majority of persons named Flavius during the later Empire could not have been descended from the Flavia gens; and indeed, the distinction between nomina and cognomina was all but lost, so that in many cases one cannot even determine with certainty whether it is a nomen or a cognomen. However, because it is impossible to determine which of these persons used Flavius as a gentile name, they have been listed below.
The Flavii of the Republic claimed Sabine ancestry, and may have been related to the Flavii who lived at Reate during the first century AD, from whom the emperor Vespasian descended; but the gentilicium is also found in other parts of Italy, such as Etruria and Lucania. The nomen Flavius is of Latin origin, and is derived from the surname Flavus, used by a number of gentes, and meaning "golden" or "golden-brown". It probably referred to the blond hair possessed by an early member of the family.
In modern use, Flavius is a personal name, and widely used in romance languages, including Italian and Spanish Flavio (fem. Flavia), French Flavien (fem. Flavie), Portuguese Flávio (fem. Flávia), and Romanian Flavius or Flaviu (fem. Flavia).
The early Flavii used the praenomina Marcus, Quintus, Gaius, and Lucius. Of these, only Gaius and Lucius are known from the family of the Fimbriae. The name Gnaeus occurs once, but as the son of a freedman of the family, and thus does not seem to be representative of the gens. The Flavii Sabini appear to have restricted themselves to the praenomen Titus alone, and distinguished their sons by the use of different surnames, usually by giving the younger sons surnames derived from their maternal ancestors.
The Flavii of the Republic used the cognomina Fimbria, Gallus, Lucanus, and Pusio. Only the Fimbriae, whose surname refers to a fringe or border, represented a distinct family. Gallus and Lucanus belong to a class of surnames derived from places of origin or association, referring to Gaul and Lucania, respectively, although Gallus, a very common surname, could also refer to a cockerel. Pusio was originally a nickname indicating a little boy, and would have been bestowed on someone small or youthful.
The Flavii Sabini, whose surname indicates Sabine ancestry, rose to prominence under the Empire. They were descended from Titus Flavius Petro, a soldier from Reate who fought under Gnaeus Pompeius Magnus. Within two generations they had attained such respectability that two of his grandsons held the consulship in consecutive years, AD 51 and 52; the younger of these marched to Rome at the head of an army in the year of the four emperors, AD 69, and claimed the imperial dignity as the emperor Vespasian. However, within less than thirty years, the family was largely destroyed through the workings of Vespasian's son, the emperor Domitian. The Flavii Titiani may be descended from the Flavii Sabini through the consul Titus Flavius Clemens, a nephew of Vespasian; the first of this branch, Titus Flavius Titianus, who was governor of Egypt from AD 126 to 133, may have been his son.
Flavius was borne by all members of Constantine's dynasty. Following its use by the Constantinian dynasty, the name assumed the attributes of an imperial title, much as Antoninus had been treated by the Severan dynasty, who followed the Antonines. It was borne by the Valentinian and Theodosian dynasties, and subsequently by barbarian rulers claiming to be their rightful successors. From the sole rule of Honorius onward, the name was not used in official contexts during the fifth century, and the few surviving examples are of transcribed imperial letters, reflecting the entrenched association of the name with the imperial office in popular perception, rather than official nomenclature. Under Justinian I, the name once again became part of the imperial nomenclature; it remained so under his successors until the time of Justinian II.
Some Roman legions were called Flavia, as they had been levied by the Flavian emperors: