the elder brother of Seneca the philosopher, who was tutor and for some time minister of the emperor Nero
He was “deputy,” i.e., proconsul, as in Revised King James Version, of Achaia, under the emperor Claudius, when Paul visited Corinth (Acts 18:12). The word used here by Luke in describing the rank of Gallio shows his accuracy. Achaia was a senatorial province under Claudius, and the governor of such a province was called a “proconsul.” He is spoken of by his contemporaries as “sweet Gallio,” and is described as a most popular and affectionate man.
When the Jews brought Paul before his tribunal on the charge of persuading “men to worship God contrary to the law” (18:13), he refused to listen to them, and “drave them from the judgment seat” (18:16).