Diocese of Adarbaigan was one of the classical East Syriac dioceses of the Church of the East. The diocese, attested between the fifth and eighth centuries, was centred on the town of Ganzak and was included in the metropolitan province of Adiabene.

The diocese of Adarbaigan appears to have covered the territory included within the Sassanian province of Atropatene. It was bounded on the west by the Salmas and Urmi plains to the west of Lake Urmi, and on the south by the diocese of Salakh, which included the districts around the modern town of Rawanduz. Its centre seems to have been the town of Ganzak. Adarbaigan was not among the dioceses assigned to a metropolitan province in 410, but by the eighth century it was part of the metropolitan province of Adiabene. The metropolitan Maranʿammeh of Adiabene, who flourished during the third quarter of the eighth century, adjusted the boundaries of the dioceses of Salakh and Adarbaigan, transferring the district of Daibur from Salakh to Adarbaigan and the district of Inner Salakh from Adarbaigan to Salakh. These boundary changes probably affected Christian communities living in the upper valley of the Lesser Zab river.^[1]

A separate East Syriac metropolitan province was created for Adarbaigan in the second half of the thirteenth century, possibly centred on Tabriz. Raiding and brigandage were rife in Mesopotamia at this period, and the creation of a new East Syriac metropolitan province reflected a migration of Christians from the Tigris plains to the relative safety of Adarbaigan, where there was a strong Mongol military presence. By the sixteenth century the title 'Adarbaigan' had been assumed by the East Syriac bishops of Salmas, doubtless reflecting a memory that the Salmas district had once been part of the diocese of Adarbaigan.

The bishop Hosea of 'Ganzak of Adarbaigan' was among the signatories of the acts of the synod of Acacius in 486.^[2]

The bishop Yohannan 'of Adarbaigan' was among the signatories of the acts of the synod of Mar Aba I in 544.^[3]

The bishop Melchisedec of Adarbaigan adhered by letter to the acts of the synod of Joseph in 554, and was among the signatories of the acts of the synod of Ezekiel in 576.^[4]

The bishop Hnanishoʿ of Adarbaigan was among the signatories of the acts of the synod of Gregory in 605.^[5]

v t e Dioceses of the Church of the East
Hierarchy divided into the Chaldean Catholic Church and the Assyrian Church of the East after the schism of 1552
Time periods	Dioceses of the Church of the East to 1318 Dioceses of the Church of the East, 1318–1552 Dioceses of the Church of the East after 1552
Interior metropolitan provinces to 1318	Adiabene Beth Garmaï Beth Huzaye Maishan Nisibis Patriarchal Province of Seleucia-Ctesiphon
Exterior metropolitan provinces to 1318	Beth Sinaye (China) Beth Tuptaye (Tibet) Dailam Damascus Fars Herat Hulwan India Islands of the Sea Kashgar and Nevaketh Katai and Ong Merv Rai Samarqand Tangut
dioceses to 1318	Abiward and Shahr Piroz Adarbaigan Al-Bariya Al-Kuj Al-Qabba Al-Rustaq Aoustan d'Arzun Armenia Ardashir Khurrah (Shiraf) Arzun ʿAïn Sipne Badisi and Qadistan Balad Barhis Beth Bgash Beth Daraye Beth Dasen Beth Lapat Beth Mazunaye (Oman) Beth Moksaye Beth Nuhadra Beth Rahimaï Beth Tabyathe and the Kartawaye Beth Waziq Beth Zabdaï Bih Shabur (Kazrun) Dabarin Dairin Darabgard Dasqarta d'Malka Delasar Dinawar Egypt Erbil Eshnuq Gawkaï Gubeans Gurgan Haditha Hagar Hamadan Hamir Harran and Callinicus Hatta Hebton Herat Hesna d'Kifa Hirta Hormizd Ardashir Hrbath Glal Ispahan Istakhr Jerusalem Jews Karka d'Beth Slokh Karka d'Ledan Karka d'Maishan Karman Kashkar Khanijar Lashom Mahoze d'Arewan Mardin Marga Marmadit Masabadan Mashkena d'Qurdu Mashmahig (Bahrain) Maʿaltha and Hnitha Merw i-Rud Meskene Mihraganqadaq Mosul Muqan Nahargur Niffar, Nil and al-Nuʿmaniya Nihawand Nineveh Piroz Shabur Prath d'Maishan Pusang Qaimar Qarta and Adarma Qasr and Nahrawan Qish Qube d'Arzun Radani Ram Hormizd Ramonin Reshʿaïna Rima Salakh Salmas Segestan Seleucia-Ctesiphon Shahpur Khwast Shahrgard Shahrzur Shenna d'Beth Ramman Shigar and Beth ʿArabaye Shushter Soqotra Susa Taimana Tahal Tamanon Tirhan Tus and Abrashahr (Nishapur) Urmi ʿUkbara Yemen and Sanaʿa Zabe
Post-1318 dioceses (See also: dioceses from 1318 to 1552 and dioceses after 1552)	Ahwaz Alqosh Amid Anzel Ardishai Atel and Bohtan ʿAmadiya ʿAqra Berwari Cyprus Erbil (East Syriac diocese) Erbil (Chaldean archeparchy) Gawar Gazarta Hakkari Jilu Kirkuk Mardin Mosul Nisibis Salmas Seert Sehna Shemsdin Tis Tuleki Zakho
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