San Thome Basilica is a Roman Catholic (Latin Rite) minor basilica in Santhome, in the city of Chennai (Madras), India. It was built in the 16th century by Portuguese explorers, and rebuilt again with the status of a cathedral by the British in 1893. The British version still stands today. It was designed in Neo-Gothic style, favoured by British architects in the late 19th century.

Christian tradition holds that St. Thomas arrived in Kerala from Israel in 52 A.D. preached between 52 A.D. and 72 A.D., when he was martyred on St. Thomas Mount.^{[citation needed]}

San Thome Basilica is the principal church of the Madras-Mylapore Catholic Archdiocese. In 1956, Pope Pius XII raised the church to the status of a Minor Basilica, and on February 11, 2006, it was declared a national shrine by the Catholic Bishops' Conference of India. The San Thome Basilica is a pilgrimage centre for Christians in India. The church also has an attached museum.

Marian grotto at San Thome Basilica

Evening view of the basilica

Santhome (Tamil: சாந்தோம்) is a locality in Mylapore in Chennai city (old Madras) in India.

The word Santhome or San Thome is derived from Saint Thomas, one of the twelve apostles of Jesus Christ. The local Christian belief is that the apostle came to India in A.D.52, was martyred in A.D.72 at St.Thomas Mount in the City and was interred in Mylapore. A church was built over his tomb and this is known as the San Thome Basilica. The Basilica is one of three churches that claim to have been built over the tomb of an apostle. The other two are St. Peter's Basilica in Rome, Italy and the church of Saint James the Great in Santiago de Compostela, Spain.

Commonly known as Santhome Church, the International Shrine of St. Thomas Basilica has an underground tomb chapel where pilgrims can pray in front of the sepulchre of St. Thomas. Superstitious people believe that sand taken from the tomb has miraculous healing powers. Marco Polo the great Venetian traveller visited the tomb in 1292 and made a record of his visit in his travel diaries: