Addai

Addai, also known as Adai, is a saint in Syriac Christian tradition, revered as one of the early Christian missionaries associated with the city of Edessa (present-day Şanlıurfa, Turkey). In most versions of the Syriac hagiography, he is an apostolic figure who, together with his companion Mari, evangelized Mesopotamia and founded the church in Edessa during the 2nd century. The exact identity of Addai is uncertain; some traditions identify him with Thaddeus the Apostle (Jude), while others treat him as a distinct figure. The surviving accounts are largely legendary and date from later centuries, and he is not listed in the canonical New Testament.

Key texts associated with Addai include the Acts of Addai and the Doctrine of Addai, both Syriac writings from late antiquity that recount his mission and the early church in Edessa. These works also describe the conversion of Edessa and, in some variants, the sending of Addai's disciples to regions beyond Edessa. The most enduring legacy attributed to Addai is the Liturgy of Addai and Mari, one of the oldest East Syriac Eucharistic prayers, still used in the liturgies of the Assyrian Church of the East, the Syriac Orthodox Church, and related communities, though the text's precise authorship remains debated.

Addai is commemorated as a saint in several Eastern churches, with feast days observed in Syriac Christian calendars. He is considered a foundational figure for the spread of East Syriac Christianity, contributing to the early development of what would become the Church of the East.