According to the Acts of the Apostles, the Synagogue of the Libertines (e.g. KJV, Wycliffe Bible) or Synagogue of the Freedmen (e.g. NKJV, NRSV) were a group of Hellenistic Jews who disputed with Saint Stephen (Acts 6:9).
The Greek text of this verse reads:
ανεστησαν δε τινες των εκ της συναγωγης της λεγομενης λιβερτινων και κυρηναιων και αλεξανδρεων και των απο κιλικιας και ασιας συζητουντες τω στεφανω.
or in English:
Then there arose certain of the synagogue, which is called the synagogue of the Libertines, and Cyrenians, and Alexandrians, and of them of Cilicia and of Asia, disputing with Stephen.
Opinion is divided as to the number of synagogues named here. The probability is that there are three, corresponding to the geographical regions involved, Rome and Italy, North East Africa, and Asia Minor. In this case the Synagogue of the Libertines is the assembly of the Freedmen from Rome, descendants of the Jews enslaved by Pompey after his conquest of Judea in 63 BC. However, λιβερτινων και κυρηναιων και αλεξανδρεων taken closely together, the first name must denote the people of some city or district. The obscure town Libertum (inferred from the title Episcopus Libertinensis in connection with the synod of Carthage, AD 411) is less likely than the reading λιβιων underlying certain Armenian versions and Syriac commentaries. The Greek towns lying west from Cyrene would naturally be called Libyan. Consequently, these returned Jews, instead of being liberalized by their residence abroad, were more tenacious of Judaism and more bitter against Stephen than those who had never left Judea.