Jacobite Syrian Christian Church in the context of "Baselios Joseph I"

The Malankara Orthodox Syrian Church (MOSC) also known as the Indian Orthodox Church (IOC) or simply as the Malankara Church, is an autocephalous Oriental Orthodox church headquartered in Devalokam, near Kottayam, India. It serves India's Saint Thomas Christian (also known as Nasrani) population. According to tradition, these communities originated in the missions of Thomas the Apostle in the 1st century (circa 52 AD). It employs the Malankara Rite, an Indian form of the West Syriac liturgical rite.

The MOSC descends from the Malankara Church and its affiliation with the Syriac Orthodox Church. However, between 1909 and 1912, a schism over the authority of the Syriac Orthodox Patriarch of Antioch resulted in the dissolution of the unified Malankara Church and establishment of the overlapping and conflicting MOSC and Jacobite Syrian Christian Church (JSCC). Since 1912, the MOSC has maintained a catholicate, the Catholicos of the East and Malankara Metropolitan of Malankara Orthodox Church–presently Baselios Marthoma Mathews III–who is the primate of the church.

The Catholicos of India, also referred to as the Catholicos of the East or the Maphrian is the head of the Jacobite Syrian Christian Church. He is ordained by the Patriarch of Antioch and functions within the Syriac Orthodox Church at an ecclesiastical-rank second to him. He presides over the Holy Synod of the Jacobite Syrian Christian Church. The current Catholicos of India is Baselios Joseph, who was elevated on March 25, 2025.

The Catholicate is considered the continuation of the historical Maphrianate of the East which was established in the 7th century, to oversee the affairs of the Syriac Orthodox Church in Persia under the jurisdiction of the Patriarchate of Antioch. It was abolished in 1860 by the Holy Synod of the Syriac Orthodox Church, and reestablished in Kerala in 1964 with the title "Catholicos" with jurisdiction over India. The Catholicos is seated at Mar Athanasius Cathedral, Puthencruz, Kerala.

A catholicos (plural: catholicoi) is the head of certain churches in some Eastern Christian traditions. The title implies autocephaly and, in some cases, it is the title of the head of an autonomous church. The word comes from 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 Church of the East, some Oriental Orthodox, Eastern Orthodox, and Eastern Catholic churches historically use this title; for example the Armenian Apostolic Church and the Georgian Orthodox Church. In the Church of the East, the title was given to the church's head, the patriarch of the Church of the East; it is still used in two successor churches, the Assyrian Church of the East and the Ancient Church of the East, the heads of which are known as catholicos-patriarchs. In the Armenian Church there are two catholicoi: the supreme catholicos of Ejmiadzin and the catholicos of Cilicia. The title catholicos-patriarchs is also used by the primate of the Armenian Catholic Church. In India, an autocephalous Oriental Orthodox Church and the regional head of Jacobite Syrian Christian Church (an autonomous Church within Syriac Orthodox Church) use this title. The first is the catholicos of the East and Malankara Metropolitan, and the latter the catholicos of India, but unequally same according to the constitution of the Syriac Orthodox Church and the Jacobite Syrian Christian Church.

The Malankara Rite is the form of the West Syriac liturgical rite practiced by several churches of the Saint Thomas Christian community in Kerala, India. West Syriac liturgy was brought to India by the Syriac Orthodox Bishop of Jerusalem, Gregorios Abdal Jaleel, in 1665; in the following decades the Malankara Rite emerged as the liturgy of the Malankara Church, one of the two churches that evolved from the split in the Saint Thomas Christian community in the 17th century. Today it is practiced by the various churches that descend from the Malankara Church, namely the Jacobite Syrian Christian Church, the Malankara Orthodox Syrian Church (Indian Orthodox Church), the Syro-Malankara Catholic Church, Malankara Mar Thoma Syrian Church, and the Malabar Independent Syrian Church.

Among these, the Jacobite Syrian Christian Church, the Malankara Orthodox Syrian Church, the Syro-Malankara Catholic Church and the Malabar Independent Syrian Church preserve the traditional West Syriac liturgy, while the Malankara Mar Thoma Syrian Church follows a reformed liturgical tradition shaped partly by Anglican influences in the 19th century.

The Malankara Church, also known as Malankara Syrian Church, was the unified body of Puthankur Saint Thomas Christians who claim origins from the missions of Thomas the Apostle. This community, under the leadership of Thoma I, opposed the Padroado Jesuits as well as the Propaganda Carmelites following the Coonan Cross Oath of 1653, which was taken to resist Western Catholic influences.

The Malankara Church eventually came under the influence of the Syriac Orthodox Church but later split successively, leading to the creation of churches across various denominations and traditions. The Malankara divisions and branchings have resulted in the present-day Jacobite Syrian Christian Church, Malankara Orthodox Syrian Church, Malankara Mar Thoma Syrian Church, Malabar Independent Syrian Church, Syro-Malankara Catholic Church, the Saint Thomas Anglicans of the Church of South India and the St. Thomas Evangelical Church of India.