Adiabene was an ancient kingdom in northern Mesopotamia, corresponding to the northwestern part of ancient Assyria. The size of the kingdom varied over time; initially encompassing an area between the Zab Rivers, it eventually gained control of Nineveh, and starting at least with the rule of Monobazos I, Gordyene became an Adiabenian dependency. It reached its zenith under Izates II, who was granted the district of Nisibis by the Parthian king Artabanus II as a reward for helping him regain his throne. Adiabene's eastern borders stopped at the Zagros Mountains, adjacent to the region of Media. Arbela served as the capital of Adiabene.
Saint Jacob of Nisibis, also known as Saint Jacob of Mygdonia, Saint Jacob the Great, and Saint James of Nisibis, was the Bishop of Nisibis until his death.
The School of Nisibis, for a time absorbed into the School of Edessa, was an educational establishment in Nisibis. It was an important spiritual centre of the early Church of the East, and like the Academy of Gondishapur, it is sometimes referred to as the world's first university. The school had three primary departments teaching: theology, philosophy and medicine. Its most famous teacher was Narsai, formerly head of the School of Edessa.
Babai the Great was an early church father of the Church of the East. He set several of the foundational pillars of the Church, revived the monastic movement, and formulated its Christology in a systematic way. He served as a monastic visitor and coadjutor with Mar Aba as unofficial heads of the Church of the East after Catholicos Gregory until 628 AD, leaving a legacy of strong discipline and deep religious Orthodoxy. He is revered in the modern Assyrian Church of the East.
Henana of Adiabene was a Christian theologian, and headmaster of the School of Nisibis, the main theological center of the Church of the East (571–610).
Ishoʿyahb III of Adiabene was Patriarch of the Church of the East from 649 to 659.
Ishoʿyahb II of Gdala was Patriarch of the Church of the East from 628 to 645. He reigned during a period of great upheaval in the Sasanian Empire. He became patriarch at the end of a disastrous war between Rome and Persia, which weakened both powers. Two years later the Moslem Arabs began a career of conquest in which they overthrew the Sassanian empire and occupied the eastern provinces of the Roman empire. Ishoʿyahb lived through this momentous period, and is said to have met both the Roman emperor Heraclius and the second Moslem caliph ʿUmar ibn al-Khattab.
The Patriarchal Province of Seleucia-Ctesiphon was an ecclesiastical province of the Church of the East, with see in Seleucia-Ctesiphon. It was attested between the fifth and thirteenth centuries. As its name entails, it was the province of the patriarch of the Church of the East. The province consisted of a number of dioceses in the region of Beth Aramaye, between Basra and Kirkuk, which were placed under the patriarch's direct supervision at the synod of Yahballaha I in 420.
The Metropolitanate of Nisibis was an East Syriac metropolitan province of the Church of the East, between the fifth and seventeenth centuries. The ecclesiastical province of Nisibis had a number of suffragan dioceses at different periods in its history, including Arzun, Beth Rahimaï, Beth Qardu, Beth Zabdaï, Qube d’Arzun, Balad, Shigar (Sinjar), Armenia, Beth Tabyathe and the Kartawaye, Harran and Callinicus (Raqqa), Maiperqat, Reshʿaïna, Qarta and Adarma, Qaimar and Hesna d'Kifa. Aoustan d'Arzun and Beth Moksaye were also suffragan dioceses in the fifth century.
Beth Huzaye or ʿIlam was an East Syriac metropolitan province of the Church of the East, between the fifth and fourteenth centuries. The metropolitan bishops of Beth Huzaye sat at Beth Lapat (Jundishapur). The metropolitan province of Beth Huzaye had a number of suffragan dioceses at different periods in its history, including Karka d'Ledan, Hormizd Ardashir, Shushter, Susa, Ispahan, Mihraganqadaq and Ram Hormizd. The diocese of Shahpur Khwast may also have been a suffragan diocese of the province of Beth Huzaye.
Metropolitanate of Adiabene was an East Syriac metropolitan province of the Church of the East between the 5th and 14th centuries, with more than fifteen known suffragan dioceses at different periods in its history. Although the name Hadyab normally connoted the region around Erbil and Mosul in present-day Iraq, the boundaries of the East Syriac metropolitan province went well beyond the Erbil and Mosul districts. Its known suffragan dioceses included Beth Bgash and Adarbaigan, well to the east of Adiabene proper.
The Metropolitanate of Merv was an East Syriac metropolitan province of the Church of the East, between the fifth and eleventh centuries, with several known suffragan dioceses.
Diocese of Kashkar, sometimes called Kaskar, was the senior diocese in the Church of the East's Province of the Patriarch. It see was in the city of Kashkar. The diocese is attested between the fourth and the twelfth centuries. The bishops of Kashkar had the privilege of guarding the patriarchal throne during the interregnum between the death of a patriarch and the appointment of his successor. As a result, they are often mentioned by name in the standard histories of the Nestorian patriarchs, so that a relatively full list of the bishops of the diocese has survived.
Ezekiel was patriarch of the Church of the East from 570 to 581. He is principally remembered in the popular tradition for having called his bishops 'the blind leading the blind', an act of presumption for which he was punished by becoming blind himself.
Maremmeh was patriarch in the Church of the East from 646 to 649.
Dadishoʿ (528/9–604) was a monk and author of the Church of the East. He was the second abbot of the great monastery of Mount Izla after its founder, Abraham of Kashkar. Giuseppe Assemani conflated him with Dadishoʿ Qaṭraya, who lived a century later.
The School of Seleucia-Ctesiphon was a theological school of the Church of the East located in the western half of the city of Seleucia-Ctesiphon on the right bank of the Tigris. It was an independent Christian school, not attached to any particular church or monastery.
Daniel bar Maryam was a historian and chronographer of the Church of the East who lived in the 7th century.
Ishoʿsabran, born Mahanosh, was a Persian Zoroastrian convert to Christianity who was martyred in the Sasanian Empire in 620 or 621. He is commemorated as a saint in the East Syriac churches on the third Friday after Annunciation.
Elias was the metropolitan bishop of Merv in the Church of the East.