God-fearers (φοβούμενοι τὸν Θεόν, phoboumenoi ton Theon) or God-worshippers (θεοσεβεῖς, Theosebeis) were a numerous class of Gentile sympathizers to Hellenistic Judaism that existed in the Greco-Roman world, which observed certain Jewish religious rites and traditions without becoming full converts to Judaism. The concept has precedents in the proselytes of the Hebrew Bible.
Many of these Greco-Roman sympathizers to Hellenistic Judaism, which had a monotheistic or henotheistic Pagan background, were worshippers of Caelus (the Roman name/equivalent to Yahweh). Some modern scholars of Judaic studies, such as A. Thomas Kraabel, believe the God-fearers named in the New Testament (such as Cornelius the Centurion) to be a fictional invention of the Acts of the Apostles. More generally, God-fearing has come to mean someone who is honestly religious.
History of the Jews in the Roman Empire and Second Temple Judaism
Since the mid-1980s, a growing number of scholars of Judaic studies and history of Judaism became interested in the subject of God-fearers and their relationship with Hellenistic Judaism and early Christianity. According to the popular opinion, Jews that lived in the Greco-Roman world during the Hellenistic and Roman period were not involved in active missionary efforts of mass conversion among Pagans, although many historians disagree.
As Jews emigrated and settled in the Roman provinces of the Empire, Judaism became an appealing religion to a number of Pagans, for many reasons; God-fearers and proselytes that underwent full conversion were Greeks or Romans, and came from all social classes: they were mostly women and freedmen (liberti), but there were also artisans, soldiers and few people of high status, like patricians and senators. Despite their allegiance to Judaism, the God-fearers were exempted from paying the "Jewish tax" (fiscus Judaicus).
The class of God-fearers existed between the 1st and the 3rd century CE.