Catholicos, plural Catholicoi, is a title used for the head of certain churches in some Eastern Christian traditions. The title implies autocephaly and in some cases is borne by the designated head of an autonomous church, in which case the holder might have other titles such as Patriarch. In other cases a catholicos heads a Particular Church and is subject to a patriarch or other church head. The word is a transliteration of the ancient Greek καθολικός, pl. καθολικοί, derived from καθ' ὅλου (kath'olou, "generally") from κατά (kata, "down") and ὅλος (holos, "whole"), meaning "concerning the whole, universal, general"; it originally designated a financial or civil office in the Roman Empire. The name of the Catholic Church is derived from the same linguistic origin.
The Church of the East, some Oriental Orthodox, Eastern Orthodox churches, and some Eastern Catholic Churches historically use this title. In the Church of the East, the title was given to the church's head, the Patriarch of the Church of the East; the title Catholicos is also used for the head of the Armenian Apostolic Church and the Georgian Orthodox Church. In the Syriac Orthodox Church the Catholicos of the East was given to the Maphrian, historically an office below the Syriac Orthodox Patriarch of Antioch.
Origin of the title 
The title came into common use with the Patriarchate of Antioch sometime after the division of jurisdiction of provinces among the three Churches in the First Council of Nicaea in 325 AD, this along with canon six confirmed the traditional jurisdiction of the Church of Antioch. In early usage, Catholicoi were created mainly to rule provinces formed outside of the Roman Empire. The actual extent of their relationship with Antioch is unclear.
The earliest ecclesiastical use of the title Catholicos was by the Catholicos of Armenia, head of the Armenian Apostolic Church, in the 4th century. Sometime later, it was adopted by the bishops of Seleucia-Ctesiphon in Persia, who became the designated heads of the Church of the East. The first claim that the bishop of Selucia-Ctesiphon was superior to the other bishoprics and had (using a later term) patriarchal rights was made by Patriarch Papa bar Gaggai (or Aggai, c. 317-c. 329). In the 5th century this was claim strengthened and Isaac (or Ishaq, 399-c.410), who organized the Council of Seleucia-Ctesiphon, used the title of bishop of Selucia-Ctesiphon, Catholicos and Head over the bishops of all the Orient. This line of Catholicos founded the Church of the East and the development of the East Syrian Rite.
Autocephalous churches of East Syrian Rite 
The following are autocephalous churches of East Syrian Rite that claim succession to the Catholicos of the East of Selucia-Ctesiphon from the Church of the East. Referred to as Nestorian in Western texts, the term Nestorian was formally renounced in 1976 by Dinkha IV.
Assyrian Church of the East 
Dinkha IV is the current Catholicos-Patriarch of the Assyrian Church of the East. One of the oldest Christian churches, it is a modern successor of the historical Church of the East, also known as the Persian Church, having emerged from a split with the Chaldean Church in the 16th century. It traces its origins to the See of Seleucia-Ctesiphon in central Mesopotamia, which tradition holds was founded by Saint Thomas the Apostle (Tooma Shlikha) as well as Saint Mari and Saint Addai in AD 33 as asserted in the Doctrine of Addai.
It is one of the three Churches of the East that hold themselves distinct from Oriental and Eastern Orthodoxy. The Assyrian Church of the East does not use the word "orthodox" in any of its service books or official correspondence, nor does it use any word which can be translated as "correct faith" or "correct doctrine," the rough translation of "orthodox". The adjectives "holy," "catholic," and "apostolic" were officially added to the Assyrian Church of the East's title in conformance with the Niceno-Constantinopolitan Creed which declares, "We believe in one, holy, catholic, and apostolic church." In this context, "holy" refers to being set apart for a purely sacred purpose; "apostolic" means founded by one of Jesus's own apostles; and "catholic" is the Greek word for "universal," indicating a worldwide church. In India, it is more often called the Chaldean Syrian Church. In the West it is often called the Nestorian Church, due to its historical associations with Nestorianism, though the church itself considers the term pejorative and argues that this association is incorrect. The church declares that no other church has suffered as many martyrdoms as the Assyrian Church of the East.
The founders of Assyrian theology were Diodorus of Tarsus and Theodore of Mopsuestia, who taught at Antioch. The normative Christology of the Assyrian church was written by Babai the Great (551–628) and is clearly distinct from the accusations directed toward Nestorius: his main christological work is called the 'Book of the Union', and in it Babai teaches that the two qnome (essences, or hypostases) are unmingled but everlastingly united in the one parsopa (personality) of Christ.
Ancient Church of the East 
Eastern Catholic Churches of East Syrian Rite 
Chaldean Catholic Church of the East 
The Chaldean Catholic Church is an Eastern church of the Catholic Church, maintaining full communion with the Bishop of Rome and the rest of the Catholic Church. It is descended from the historical Church of the East and became independent following a 16th-century split with the Church of the East. The Chaldean Catholic Church presently has an estimated 2.5 million Chaldean Christian members. They are indigenous people of Iraq and descended from the ancient Mesopotamians. They retain Aramaic as a native tongue.
Eastern Catholic Churches of West Syrian Rite 
Syro-Malankara Catholic Church 
The Syro-Malankara Catholic Church which was raised to the status of a Major Archiepiscopal Church sui iuris on February 10, 2005 received the supra archiepiscopal title of Catholicos according to the tradition of Malankara Church and according to the norms of Motu Proprio "Cleri Sanctitati" Can. 335. The Holy See of Rome has approved of this by giving recognitio to the "Code of Particular Canons of the Syro-Malankara Catholic Church" which very well illustrates the title Catholicos according to the tradition and history of the Syro-Malankara Catholic Church.
Oriental Orthodox Church 
In the 6th century, on the initiative of Jacob Baradaeus, a hierarchy of the Syrian Orthodox was erected in the area now known as Iraq to serve the Christians who were not placed under the Catholicate of the Church of the East. The main See was located in Tikrit and the rite used was that of Antioch, i.e. the West Syrian Rite. The first head of this hierarchy was the Great Metropolitan Ahudemeh (559-575). The title used from about the 7th century was Maphrian (or Maphryono). In the 12th century the See was moved to Mosul and in the 13th century the title became Catholicos of the East. After the massacres of Tamerlane, the Maphrian was forced to leave Persia and this title was used for the general vicar, with nominal right of succession, for the Patriarch of the Syrian Orthodox Church.
In the 17th century many Christians of the Kerala region in India decided to leave the Church of Malabar—the local Church that had been connected to the Church of the East and since the second half of 16th century was under Portuguese control—and to align themselves under the hierarchy of the Syriac Orthodox Church. They moved from the East Syrian Rite and adopted the West Syrian Rite. The title of Catholicos of the East as an Indian hierarchy was used from the 20th century.The following heads of the Orthodox Church claim succession to the Catholicos of the East.
Malankara Orthodox Syrian Church 
Baselios Marthoma Paulose II is the current Catholicos of the Malankara Orthodox Syrian Church and is based at Devalokam near Kottayam in Kerala State.
His title is Catholicos of the East and Malankara Metropolitan of Malankara Orthodox Syrian Church also called Indian Orthodox Church.
Jacobite Syrian Orthodox Church 
Baselios Thomas I is the current Catholicos of the Jacobite Syrian Orthodox church and is based at Puthencruz near Ernakulam in Kerala State. This Church in India is under the Holy See of Syriac Orthodox Church of Antioch headed by HH Ignatius Zakka 1 Iwas (The Patriarch) based at Damascus in Syria.
His title is Catholicos of The East and also as Catholicose of India.
Ethiopian Orthodox Tewahedo Church 
In 1959, the Coptic Orthodox Church of Alexandria granted autocephaly to the Ethiopian Orthodox Tewahedo Church. Abuna Basilios was consecrated the first Patriarch Catholicos of the Ethiopian Church by the Coptic Pope Cyril VI at St. Mark's Cathedral in Cairo on 28 June 1959. The title is "Patriarch and Catholicos of Ethiopia, Ichege of the See of St. Tekle Haymanot, Archbishop of Axum".
Armenian churches 
Armenian Apostolic Church 
The head of the One Holy Universal Apostolic Orthodox Armenian Church bears the title Catholicos.
The Catholicos of Etchmiadzin presides over the Supreme Spiritual Council of the Armenian Apostolic Church and is the head of the world's 7 million Armenian Orthodox Christians.
- Catholicos of Etchmiadzin (Chief Shepherd and Pontiff to all Armenians dispersed throughout the world) of the Armenian Apostolic Church,
- Karekin II is the current Catholicos of the Armenian Apostolic Church.
- Catholicossate of the Great House of Cilicia (Since 1441).
- Aram I is the present Catholicos of the Great House of Cilicia
The primacy of honour of the Catholicossate of Etchmiadzin has always been recognized by the Catholicossate of Cilicia.
There once was a Catholicos in Akhtamar, a position that has since been abolished:
Armenian Catholic Church 
- Catholicos of the Armenian Catholic Church (in full Communion with the Pope).
Georgian Orthodox Church 
The title of catholicos is also used in the Georgian Church, whose head carries the title Catholicos-Patriarch of All Georgia.
- Catholicos of Georgian Orthodox Church
- Ilia II is the current(as of 22 February 2012) Catholicos of the Georgian Orthodox Church.
Caucasian Albania 
Historically, the title of Catholicos was also used by the chief bishop of Caucasian Albania. With the Islamic invasion this church deteriorated and the provinces came under the Catholicos of Etchmiadzin[clarification needed].
See also 
- Catholicos of Armenia
- List of Catholicoi of Armenia
- Catholicos of Georgia
- Catholicos of the East
- List of Catholicos of the East
- List of Caucasian Albanian Catholicoi
- Wigram, p. 91.
- The Motu Proprio Cleri Sanctitati Canon 335
- text of canon 6 of the First Council of Nicaea
- Yar-Shater, Ehsan; Fisher, W. B. (1983). The Seleucid, Parthian and Sasanian periods. p. 931. ISBN 978-0-521-24693-4. Retrieved 2009-02-22.
- The Syro-Malankara Catholic Church, The Code of Particular Canons of the Syro-Malankara Catholic Church, Major Archiepiscopal Curia, Trivandrum, 2012, xi
- King, Archdale (1997) [1947/8]. The Rites of Eastern Christendom. p. 84. ISBN 978-1-59333-391-1.
- Official Website of the Armenian Church
- Wigram, W. A. (2004). An introduction to the history of the Assyrian Church, or, The Church of the Sassanid Persian Empire, 100–640 A.D. Gorgias Press. ISBN 1-59333-103-7.