Founder of the church at Edessa. He was allegedly one of the seventy disciples of Jesus sent to King Abgar V Ukkama by the Apostle Thomas after the Ascension. Eusebius records the legend and calls Addai “Thaddaeus.” The Syriac [[Doctrina Addaei]] was published in 1876. The conversion of King Abgar IX (179-216) points more reliably to evangelism at Edessa, possibly in the late second century, by a Jewish Christian Addai (Baus, Handbook of Church History, vol. 1, p.207).

See Abgar, Legend of.