The CSI Tiruchirappalli Thanjavur Diocese is a diocese of Church of South India in Tamil Nadu state of India. The diocese is one among the 24 dioceses of Church of South India and was one of the first 14 dioceses to be formed at the inaugural of the Church of South India in 1947
The diocese spreads over the Mayiladuthurai district, Nagapattinam District, Tiruvarur District, Thanjavur District, Tiruchirappalli District, a part of Perambalur District, Karur District, a part of Tirupur district, a part of Coimbatore District, a part of Cuddalore District, a part of Pudukottai District, a part of Ariyalur District and part of the Union Territory of Puducherry & Karaikal. For administration purposes the diocese is subdivided into six District Church Councils(DCC) - Thanjavur DCC, Tiruchirappalli DCC, Perambalur DCC, Karur DCC, Dharapuram DCC and the Anaimalai Hills DCC. The diocese had a membership of 88,831 in 2000 and the mission in the diocese is carried through 100+ ordained pastors along with a bishop. The diocese has partnership with Leicester in The United Kingdom. Empowerment of women and dalits are the main thrusts of the diocese.