The Chaldean Syrian Church of India is an Eastern Christian Church primarily based in Thrissur, India. It is an archbishopric of the Holy Apostolic Catholic Assyrian Church of the East and is in full communion with Patriarch Gewargis III, the Catholicos-Patriarch of the Assyrian Church of the East. The Chaldean Syrian Church uses the Divine Liturgy of Saints Mar Addai and Mar Mari belonging to the East Syriac Rite liturgy. Its individuals are part of the St. Thomas Christian community, who hint their origins to the evangelistic interest of Thomas the Apostle within the 1st century.
They are almost exclusively primarily based within the kingdom of Kerala, with the church's cathedral, the Marth Mariam Cathedral, located in Thrissur. The Chaldean Syrian Church is the cutting-edge day continuation of the historical Church of the East in India, after the general public of its followers had been converted to Catholicism and West Syriac Rite Oriental Orthodoxy. Today the Chaldean Syrian Church is one of four archbishoporics inside the Assyrian Church of the East, and has about 50,000 individuals in and around Thrissur.