Saint Thomas Christians, also called Nasrani, are an ancient Christian community of India's Malabar Coast, in present day Kerala, who trace their origin to the Apostle Thomas, said by tradition to have landed at the port of Muziris in 52 CE, founded seven churches among the region's population, and been martyred near Chennai on India's east coast. The tradition's basic plausibility rests on well documented first century trade routes between Roman Egypt and southern India, sustained by sailors' knowledge of the seasonal monsoon winds, which made a voyage of the kind the tradition describes entirely feasible for the period even though no contemporary written record of Thomas's own journey survives.
External evidence for an Indian Christian community appears clearly by the fourth and sixth centuries. Writers connected to the Alexandrian Christian tradition mention Christians in India in the fourth century, and the sixth century merchant turned monk Cosmas Indicopleustes describes, in his own eyewitness account, a Christian community on the Malabar coast under a bishop consecrated in Persia, confirming that by his time the community was long established and already connected to the East Syriac, or Church of the East, hierarchy centered in Mesopotamia, a relationship that shaped its liturgy, language and governance for the following thousand years.