Ancient Church of the East
Cathedral of the Virgin Mary Baghdad, Iraq
Abbreviation	ACE
Classification	Eastern Christianity
Orientation	Syriac Christianity
Catholicos-Patriarch	Gewargis III Younan
Language	Syriac
Liturgy	East Syriac Rite
Headquarters	Baghdad, Iraq
Separated from	Assyrian Church of the East
Members	approx. 75,000, of which 45,000 are in Iraq and 20,000 in India (1999)[1]

The Ancient Church of the East (ACE) is an Eastern Christian denomination. It branched from the Assyrian Church of the East in 1964, under the leadership of Mar Toma Darmo (d. 1969). It is one of three Assyrian Churches that claim continuity with the historical Church of the East (the ancient Patriarchal Province of Seleucia-Ctesiphon), the others being the Assyrian Church of the East and the Chaldean Catholic Church. Since 1969, the see of the Ancient Church of the East is headquartered in Baghdad.^[1]

This section needs to be updated. Please help update this article to reflect recent events or newly available information. (November 2023)

In 1964, a decision by Patriarch Mar Shimun XXIII Eshai of the Assyrian Church of the East to switch over from the traditional Julian calendar to the Gregorian calendar led part of the Church of the East, to split off in a schism. The breakaway group called itself the Ancient Church of the East and in 1968 consecrated their own patriarch, Mar Toma Darmo, who strongly opposed to the system of hereditary succession of the position of patriarch of the Church of the East, as well as its adoption of the Gregorian calendar "and other modernizing measures". Mar Darmo was also joined by "various other groups opposed to Mar Shimun."^[1]

Mar Yacob III Daniel was elected as new patriarch in June 2022.^[2] However, he abdicated two months later in August 2022,^[3] and on 12 November 2022 the Holy Synod elected Mar Gewargis Younan to take his place. The consecration of the patriarch-elect was scheduled to take place in Baghdad in June 2023,^[4] and on 9 June, Mar Gewargis III Younan was consecrated as the 110th Patriarch of the Ancient Church of The East.

The Holy Synod is listed as follow:

• Mar Gewargis III Younan, Catholicos-Patriarch of the Whole World (seat in Baghdad, Iraq)
• Mar Yacob Daniel, Metropolitan of the Archdiocese of Baghdad and Basra (seat in Baghdad and Basra)
• Mar Zaia Khoshaba, Metropolitan of the Archdiocese of Canada and the United States (seat in Toronto, Canada)
• Mar Toma Aramia, Metropolitan who resides in Canada (seat in Toronto, Canada)
• Mar Shimun Daniel Alkhoury,^[5] Bishop of Iraq and the Middle East.

• Thoma Darmo (1968–1969)
• Addai II Giwargis (1972–2022)
• Yacob III Daniel (2022–2022)
• Gewargis III Younan (9 June 2023^[6] – present)

Under the tenure of Addai II, the Ancient Church of the East has made several gestures towards reunification with the Assyrian Church of the East. The most prominent of these is undoubtedly the declaration made in June 2010 stating that the Ancient Church of the East would now celebrate Christmas in accordance with the Gregorian calendar. Previously, the church used the traditional Julian date for the Christmas Day (December 25 of the Julian calendar currently corresponds to January 7 of the Gregorian Calendar), as the Church of the East had throughout its history. The decision was to be implemented later that year, on December 25, 2010.^[7]

Following the death (March 2015) of Dinkha IV, Catholicos-Patriarch of the Assyrian Church of the East,^[8] dialogue of unification continued between the churches.

On May 22, 2015, a meeting involving prelates of both Holy Councils took place in Chicago, Illinois, in the library of St. Andrew's Assyrian Church of the East. Present were Yacoub Daniel, Zaia Khoshaba, and Gewargis Younan representing the Ancient Church of the East, and Gewargis Sliwa, Awa Royel, and Iskhaq Yousif representing the Assyrian Church of the East. Archdeacon William Toma served as the meeting's common secretary. Yacoub Daniel flew in from Australia for the meeting, and Zaia traveled from Canada.^[9]

On June 1, 2015, the Holy Synod of the Assyrian Church of the East met in Erbil, Iraq, to discuss the future of the church. The date had previously been arranged for the election of the new Catholicos-Patriarch. Awa Royel issued a statement on the same day, notifying the public that a response to the Ancient Church of the East's recommendations for reunification had been delivered to their prelates. The letter requested a prompt response to the terms, and the election of the new Patriarch was suspended until the following week, on June 8, 2015.^[10]

On June 5, 2015, Aprem Mooken issued a formal statement announcing that the election of the next Catholicos-Patriarch of the Assyrian Church of the East was suspended until September (2015), pending the unification of the churches.^[11]

It turned out that unification was not achievable. On 18 September, Assyrian Church of the East elected Gewargis III as the new head of the Church, and he was consecrated and enthroned as Catholicos-Patriarch on 27 September 2015.^[12]

In spite of the fact that unification was not achieved, leaders of both Churches have continued to promote various forms of mutual cooperation.^[13]

After the death of Mar Addai II, reunification failed in May 2022 and the election of a new patriarch was therefore launched.^[14][15]

• Assyrian people
• Chaldean Catholic Church
• Chaldean Syrian Church
• Church of the East
• East Syrian Rite

• Mooken, Aprem (2003). The History of the Assyrian Church of the East in the Twentieth Century. Kottayam: St. Ephrem Ecumenical Research Institute.
• Hage, Wolfgang (2007). Das orientalische Christentum. Stuttgart: Kohlhammer Verlag. ISBN 9783170176683.
• Coakley, James F. (1996). "The Church of the East since 1914" (PDF). Bulletin of the John Rylands Library. 78 (3): 179–198. doi:10.7227/BJRL.78.3.14.