|Easton's Bible Dictionary|
Safe in strength, the chief ruler of the synagogue at Corinth, who was seized and beaten by the mob in the presence of Gallio, the Roman governor, when he refused to proceed against Paul at the instigation of the Jews (Acts 18:12-17). The motives of this assault against Sosthenes are not recorded, nor is it mentioned whether it was made by Greeks or Romans. Some identify him, but without sufficient grounds, with one whom Paul calls "Sosthenes our brother," a convert to the faith (1 Corinthians 1:1).
Int. Standard Bible Encyclopedia
sos'-the-nez (Sosthenes): Chief of the synagogue at Corinth (Acts 18:17). Possibly identical with the co-worker (afterward) of Paul mentioned in 1 Corinthians 1:1.
Sosthenes (2 Occurrences)
Acts 18:17 Then all the Greeks laid hold on Sosthenes, the ruler of the synagogue, and beat him before the judgment seat. Gallio didn't care about any of these things. (WEB KJV WEY ASV BBE DBY WBS YLT NAS NIV)
1 Corinthians 1:1 Paul, called to be an apostle of Jesus Christ through the will of God, and our brother Sosthenes, (WEB KJV WEY ASV BBE DBY WBS YLT NAS NIV)