Established in 1979 from the Diocese of Madras, the Diocese of Calcutta serves eastern and north-eastern India and Kuwait, and has diminished with the emigration of its faithful.
The diocese for regions outside Kerala (Bahya Kerala Bhadrasanam) was formed in 1938. In 1976, by Catholicos Order No. 58/76, it was divided into the dioceses of Bombay, Madras and Delhi. The territory of the present Diocese of Calcutta was then part of Madras, led at the time by Dr. Stephanos Mar Theodosius. Madras at that time comprised Andhra Pradesh, Assam, Bihar, parts of Madhya Pradesh, most of Tamil Nadu, West Bengal, the Andaman and Nicobar Islands, and, overseas, Malaysia and Singapore.
On 30 October 1978 the Managing Committee resolved, with the approval of the Episcopal Synod, to reorganise the three outside-Kerala dioceses into five because of their large geographical extent. The new dioceses of America, Calcutta and Trivandrum came into effect on 1 January 1979 by order of 8 December 1978. Calcutta was assigned Assam, Bihar, Madhya Pradesh, Manipur, Meghalaya, Nagaland, Orissa, Tripura, West Bengal, Mizoram, Arunachal Pradesh and Nagpur in Maharashtra, and overseas Ahmadi, Kuwait, Muscat and Salalah. Dr. Stephanos Mar Theodosius became its first Metropolitan and led it until his death on 5 November 2007. The Catholicos then assumed charge, assisted by H.G. Geevarghese Mar Coorilos of Bombay, until H.G. Dr. Joseph Mar Dionysius became Metropolitan in March 2009.
In 2009 the outside-Kerala dioceses were further reorganised into nine, with the formation of Bangalore, Ahmedabad, Brahmavar, Northeast America, Southwest America, and UK–Europe–Africa. The parishes of the Malwa region of Madhya Pradesh and those in Oman were transferred to the new Diocese of Ahmedabad, leaving Kuwait as the only overseas territory of Calcutta. In recent decades the diocese has contracted considerably, as migration to eastern India has declined and its faithful have emigrated abroad.
5 districts, listed alphabetically.