Nehardea or Nehardeah (Aramaic: נהרדעא nher-daʻă‎‎ "river of knowledge") was a city of Babylonia, situated at or near the junction of the Euphrates with the Nahr Malka (also known as Nâr Sharri, Ar-Malcha, Nahr el-Malik, and King's Canal), one of the earliest centers of Babylonian Judaism. As the seat of the exilarch it traced its origin back to King Jehoiachin. According to Sherira Gaon (Letter of Sherira Gaon, in Neubauer, M. J. C. i. 26), Jehoiachin and his coexilarchs built a synagogue at Nehardea, for the foundation of which they used earth and stones which they had brought, in accordance with the words of Psalms 102:15, from Jerusalem (comp. a similar statement in regard to the founding of the Jewish neighbourhood in the Persian city of Ispahan, in Monatsschrift, 1873, pp. 129, 181).