In a land area of 21,051 square kilometers, the diocesan territory covers four districts of Mysore, Mandya, Coorg and Chamarajanagara. It is surrounded by the archdiocese of Bangalore, dioceses of Ooty, Calicut, Mangalore and Chikmagalur.
In the territory of Mysore diocese, the population is 10,575,780 at end of 2016.
The mission of Mysore was separated from the vicariate apostolic of Pondicherry on March 16, 1845. In 1886, the vicariate of Mysore was elevated to a diocese.
Until 1940, the diocese of Mysore included the entire districts of Mysore, Coorg and Kollegal, but on Feb. 13, 1940, Bangalore was separated from Mysore and the former bishop Mysore diocese Bishop M.B. Despatures was given charge of the new diocese, comprising the districts of Bangalore, Kolar, Tumkur and Chitradurga.
Originally Mysore belonged to the archdiocese of Goa. The district came under the Foreign Mission Society of Paris in 1776. Mysore was included in the vicariate of the Coromandel Coast (Pondicherry), erected in 1836, but was separated in 1845, and erected into a distinct vicariate apostolic in 1850.
The diocese of Mysore was reconstituted in 1941 with the addition of the Nilgiris district and part of the Coimbatore district.
However 15 years later, on July 3, 1955, Nilgiris and Coimbatore were again separated from Mysore and erected into diocese of Ootacamund (Ooty) in Tamil Nadu.
On Nov. 16, 1963, three most districts, Chikmagalur, Hassan and Shimoga were separated from the Mysore diocese to form the diocese of Chikmagalur.