Osrhoene is a region between the Euphrates and Tigris rivers whose capital was edessa. During the first two Christian centuries it was a small kingdom under the dynasty of Abgar. In 216 the Emperor Caracalla incorporated it into the Roman Empire as a province. Christianity had been introduced into Osrhoene early, most probably from Antioch by Jewish Christians. There is no historical foundation for the legends of abgar, King of Osrhoene, recorded by Eusebius (Hist. eccl. 1.12–13) to the effect that the king begged Jesus to come and heal his daughter. To this request Jesus was alleged to have sent a written reply saying that he was going to send his disciple, Thaddeus (Thaddai), to heal the girl and preach the Gospel. However, according to trustworthy sources, there were Christians in Osrhoene as early as the latter half of the 2nd century.
The Epitaph of abercius and information in Eusebius (Ecclesiastical History 5.24) witness to the fact that counsel was sought from the Diocese of Osrhoene in the matter of the fixing of the date for Easter. At the beginning of the 3rd century julius africanus found the heretic bardesanes in the court of King Abgar IX. There is no conclusive evidence for A. von harnack's contention that this king embraced Christianity and that Osrhoene was the first Christian kingdom. The Christians of Osrhoene wrote in Syriac; their greatest glory was St. ephrem.
Bibliography: j. p. martin, Les Origines de l'Église d'Édesse et des églises syriennes (Paris 1889). i. ortiz de urbina, "Le origini del cristianesimo in Edessa," Gregorianum, 15 (1934) 82–91.
[i. ortiz de urbina]