Christianity is India's third-largest religion with about 26 million adherents, making up 2.3 percent of the population as of the 2011 census. The written records of the Saint Thomas Christians state that Christianity was introduced in the Indian subcontinent by Thomas the Apostle, who sailed to the Malabar region in the present-day Kerala state in 52 AD.
The Acts of Thomas mentions that the early Christians were Malabarese Jews, who had settled in India before the birth of Christ. Apostle Thomas, an Aramaic-speaking Jew from Galilee (present-day Israel) and one of the disciples of Jesus, came to India in search of Indian Jews. Following years of evangelising, Thomas was martyred and his remains were buried at St. Thomas Mount in Mylapore. A scholarly consensus exists that Christian communities had firmly established in the Malabar by 600 AD at the latest. These communities were composed mainly of Nestorians, belonging to the Church of the East in India, that used the East Syriac Rite.
Following the discovery of a sea route to India by the Portuguese explorer Vasco da Gama in the 15th century AD, Western Christianity was established in the European colonies of Goa, Tranquebar, Bombay, Madras, and Pondicherry in the form of the Catholic Church (particularly its Latin Church) and Protestantism. Christian missionaries introduced western educational system to the Indian subcontinent to spread Christianity and campaigned for social reforms.
The Church of North India, the Church of Pakistan, and the Church of South India are united Protestant Churches that were established as a result of evangelism and ecumenism by Anglicans, Methodists, and other Protestants in India who flourished in colonial India.
Christians were active in the Indian National Congress and the Indian independence movement. The All India Conference of Indian Christians advocated for swaraj (self rule) and opposed the partition of India.
Along with native Christians, small Eurasian Christian communities such as Anglo-Indians, Luso-Indians, Armenian Indians, and others had also existed in the subcontinent.