Mar Thoma Syrian Church

The Malankara Mar Thoma Syrian Church, often shortened to Mar Thoma Church, and known also as the Reformed Syrian Church and the Mar Thoma Syrian Church of Malabar, is an autonomous Oriental Protestant Christian church based in Kerala, India. While continuing many of the Syriac high church practices, the church is Protestant in its theology and doctrines. It employs a reformed variant of the West Syriac Rite Divine Liturgy of Saint James, translated to Malayalam.

The Mar Thoma Church sees itself as continuation of the Saint Thomas Christians, a community traditionally believed to have been founded in the first century by Thomas the Apostle, who is known as Mar Thoma (Saint Thomas) in Syriac, and describes itself as "Apostolic in origin, Universal in nature, Biblical in faith, Evangelical in principle, Ecumenical in outlook, Oriental in worship, Democratic in function, and Episcopal in character".

Until the beginning of the 20th century, Mar Thoma Christians lived in a few districts of Central Travancore (Pathanamthitta, Kollam, and Thiruvananthapuram districts) and Kunnamkulam (Thrissur district) in Kerala. Since that time they have spread with the 20th-century Indian diaspora to North America, Europe, the Middle East, Malaysia, Singapore, South Africa, Australia and New Zealand. According to the figures provided by the church itself, it currently has over 1 million members. Their mother tongue is Malayalam, the language of Kerala, and historically the variety known as Suriyani Malayalam was associated with them.

According to the 2011 Census of Kerala it was, with a membership of 405,089, the sixth largest Christian church in the state, coming after the Syro-Malabar Catholic Church (2,345,911), the Latin Catholic Church (932,733), the Malankara Orthodox Syrian Church (493,858), the Jacobite Syrian Christian Church (482,762), and the Syro-Malankara Catholic Church (465,207).