EDESSA, or CALLIRRHOE, a city in the north of Mesopotamia, in the province of Osroene, on the banks of the small river Scirtus, a tributary of the Euphrates. The time and manner of the foundation of this city are very variously given by different authors: by some writers its origin is even referred to Nimrod; and though this account may be very safely rejected, yet the extreme antiquity of the place is undeniable. Its very position is also variously given by the ancient geographers. Strabo, for instance, confounding it with Hierapolis, places it in Syria, while Pliny makes mention of it as being in Arabia.
It was not till the Christian era that Edessa began to play a part in history. In the wars between the Eastern empire and the Persians, and in the early history of the church, the name of Edessa very frequently occurs. One of the most important theological schools of the primitive church had its seat in this city, and distinguished itself by the zeal with which it maintained the Nestorian heresy. This zeal ultimately proved the ruin of the school, whose professors were banished from Edessa by the orthodox bishop Martyrus, while the building in which they had taught was pulled down by order of the emperor Zeno, towards the end of the fifth century.
In the wars with the Persians, Edessa frequently suffered great damage; and though this was immediately repaired, yet the destructive inundations of the Scirtus on more than one occasion threatened to endanger the very existence of the town. In 718 Edessa was nearly destroyed by an earthquake; and in 1184 it fell into the hands of the Saracens, under whose rule its prosperity rapidly declined. Under the name of Orfah, Edessa has recovered to a certain extent its ancient greatness, as it stands on the great route between Kurdistan and Aleppo, and has consequently become a place of very considerable commercial importance.