Manbij (Arabic: منبج‎ Manbiǧ, Classical Syriac: ܡܒܘܓ‎ mabbug) is a town in the Aleppo Governorate, Syria, 30 kilometers west of the Euphrates. In the 2004 census by the Central Bureau of Statistics (CBS), Manbij had a population of nearly 100,000.

The ruins of the ancient city "Hierapolis Bambyce," also known as "Hierapolis Euphratensis" or "Hierapolis in Euphratesia", are 20 km north, where remains of aqueducts and the Byzantine walls of Justinian are still to be seen.

The place first appears in Greek as Bambyce, but Pliny (v. 23) tells us its Syrian name was Mabog (also Mabbog, Mabbogh). As a centre of the worship of the Syrian goddess Atargatis, it became known to the Greeks as the Ἱερόπολις (Hieropolis) 'city of the sanctuary', and finally as Ἱεράπολις (Hierapolis) 'holy city'.

This worship of Atargatis was immortalized in De Dea Syria which has traditionally been attributed to Lucian of Samosata, a native of Commagene, who gave a full description of the religious cult of the shrine and the tank of sacred fish of Atargatis, of which Aelian also relates marvels. According to the De Dea Syria, the worship was of a phallic character, votaries offering little male figures of wood and bronze. There were also huge phalli set up like obelisks before the temple, which were ceremoniously climbed once a year and decorated.