Malankara Orthodox Syrian Church

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 traces its origin to the historic Malankara Church and its association with the Syriac Orthodox Church. Between 1909 and 1912, differences regarding the extent of authority of the Patriarch of Antioch led to a division within the Malankara Church. As a result, two ecclesiastical bodies emerged: the Malankara Orthodox Syrian Church (MOSC) and the Jacobite Syrian Christian Church (JSCC), both of which claim continuity with the Malankara Christian tradition.

Since 1912, the MOSC has maintained the office of the Catholicos of the East, who also holds the title of Malankara Metropolitan. The current Catholicos and Malankara Metropolitan is Baselios Marthoma Mathews III, who serves as the primate of the church. In 1934, the MOSC adopted a constitution to systematize the function and administration of the church. It defined the conditional authority of the Patriarch of Antioch, and vested the powers of temporal and spiritual administration in the supreme hierarch who possesses the offices of the Catholicate and the Malankara Metropolitanate.

The Malankara Orthodox Syrian Church is in communion with the other Oriental Orthodox Churches. Despite multiple efforts toward reconciliation, disputes between the MOSC and the JSCC, primarily concerning ecclesiastical authority and administrative matters, have continued, including legal proceedings and local conflicts.

The Malankara Orthodox Syrian Church accepts miaphysitism, (not to be confused with monophysitism), which holds that in the one person of Jesus Christ, divinity and humanity are united in one (μία, mia) nature (φύσις – "physis") without separation, without confusion, without alteration and without mixing where Christ is consubstantial with God the Father. Around 500 bishops within the Patriarchates of Alexandria, Antioch and Jerusalem refused to accept the dyophysitism (two natures) doctrine decreed by the 4th ecumenical council, the Council of Chalcedon in 451, an incident that resulted in the second major split in the main body of the Christian Church (after the Nestorian schism). While the Oriental Orthodox churches rejected the Chalcedonian definition, the sees that would later become the Catholic Church and the Eastern Orthodox Church accepted this council.

Self-reporting roughly 2.5 million members (with external estimates of roughly 1 million) across 32 dioceses worldwide, a significant proportion of the Malankara Orthodox Syrian Church's adherents reside in the southern India state of Kerala with the Malankara communities in North America, Europe, the Middle East, Malaysia, Singapore, Sri Lanka, South America, Australia and New Zealand. The Encyclopedia of Christianity Online estimated the church has approximately 1.2 million members.