Gallio, the son of the rhetoricianSeneca the Elder and the elder brother of Seneca the Younger, was born in Corduba c. 5 BC. He was adopted by Lucius Junius Gallio, a rhetorician of some repute, from whom he took the name of Junius Gallio. His brother Seneca, who dedicated to him the treatises De Ira and De Vita Beata, speaks of the charm of his disposition, also alluded to by the poet Statius. It is probable that he was banished to Corsica with his brother, and that they returned together to Rome when Agrippina selected Seneca to be tutor to Nero. Towards the close of the reign of Claudius, Gallio was proconsul of the newly-constituted senatorial province of Achaea, but seems to have been compelled by ill-health to resign the post within a few years. He was referred to by Claudius as "my friend and proconsul" in the Delphi Inscription, circa 52. Gallio was a suffect consul in the mid-50s and Cassius Dio records that he introduced Nero's performances. Not long after the death of his brother, Seneca, Gallio was attacked in the Senate by Salienus Clemens, who accused him of being a "parricide and public enemy", though the Senate unanimously appealed to Salienus not to profit "from public misfortunes to satisfy a private animosity". He did not survive this reprieve long. When his second brother, Annaeus Mela, opened his veins after being accused of involvement in a conspiracy, Gallio seems to have committed suicide, perhaps under instruction in 65 AD at the age of 64.
According to the Book of Acts he dismissed the charge brought by the Jews against the ApostlePaul. His behaviour on this occasion showed his disregard for Jewish sensitivities, and also the impartial attitude of Roman officials towards Christianity in its early days. Gallio's tenure can be fairly accurately dated to between 51-52 AD. Therefore, the events of Acts 18 can be dated to this period. This is significant because it is the most accurately known date in the life of Paul.
Bruce Winter, "Rehabilitating Gallio and his Judgement in Acts 18:14-15", Tyndale Bulletin 57.2 291-308.
Sir W. M. Ramsay, St Paul the Traveller, pp. 257–261
An interesting reconstruction is given by Anatole France in Sur la pierre blanche.
F. L. Lucas's story “The Hydra ” in The Woman Clothed with the Sun, and other stories focuses on Gallio at the time of Paul's trial. "A Greek trader, a chance acquaintance of Judas Iscariot, comes to tell the Roman Governor of Corinth 'the real truth about this religious quarrel among the Jews', but is dissuaded by the tolerant old man from taking risks for Truth".
