The Diocese of Saint Thomas of Mylapore, presently in Chennai, Tamil Nadu (or in Portuguese São Tomé de Meliapor, in Latin Sancti Thomae de Meliapor), was a suffragan diocese in the ecclesiastical province of the primatial See of Goa in India.
It was located in Mylapore, and derives its name from the site of its cathedral in which the Apostle St. Thomas was reportedly interred on the site of his martyrdom and the Tamil word Mailapur (i.e. the town of peacocks), which the Greeks rendered as Maliarpha, the Portuguese as Meliapor, and the English as Mylapore.
According to local tradition amongst Saint Thomas Christians, the Apostle Thomas arrived in India, supposedly at Tamilakam, now the Indian state of Kerala, in 52 AD. According to the tradition, Thomas later moved to the east coast of South India, fixing his see at the city of Mylapore, now Chennai, Tamil Nadu
Having aroused the hostility of the local priests by making converts, Thomas fled to St. Thomas's Mount four miles (6 km) southwest of Mylapore. He was supposedly followed by his persecutors, who transfixed him with a lance as he prayed, kneeling on a stone, AD 72. His body was brought to Mylapore and buried inside the church he had built there. The present Santhome Church is on this spot but is clearly of a much later date. The Acts of Thomas and oral traditions (only recorded in writing centuries later) provide weak and unreliable evidence.