Land of Onias

The Land of Onias (Koinē Greek: Ὀνίας) is the name given in Hellenistic Egyptian, Jewish, and Roman sources to an area in ancient Egypt's Nile Delta where a large number of Jews settled. The Land of Onias, which included the city of Leontopolis (Λεόντων πόλις), was located in the Heliopolite Nome (Hebrew: אֹן ʾOn "Heliopolis).

While accounts differ on the details, it is known that the Jews of Leontopolis had a functioning temple, distinct from and contemporary to the Temple in Jerusalem, presided over by kohenim (priests) and High Priests of the family of Onias III or Onias IV, for whom the "Land of Onias" is named. Aside from a somewhat uncertain allusion of the Hellenist Artapanus of Alexandria, only Josephus gives information about this temple.

The Talmudic accounts are internally contradictory. The establishment of a central sanctuary in Egypt was probably undertaken in response, in part, to the disorders that arose in Judea under Antiochus IV Epiphanes, the desecration and sealing up of the Second Temple under his reign and, the supplanting of the legitimate family of priests by the installation of Alcimus, the personal ambition of Onias IV, and the vast extent of the Jewish diaspora in Egypt that created a demand for a sanctuary of this nature.

at its pinnacle Onias’ Temple was a major religious and cultural center of Egyptian Judaism. This assumption is bolstered by the circumstance that several works of Jewish-Hellenistic literature such as 3 Maccabees, Pseudo-Hecataeus, Joseph & Aseneth, and several oracles of the Third Book of the Sibylline Oracles appear to have been written in the milieu of the Oniad Temple.

— Meron-Martin Piotrkowski, Priests in Exile