Zoroastrian tradition, most fully preserved in a sixteenth century Persian narrative poem called the Qissa-i Sanjan, the Story of Sanjan, describes a group of Zoroastrians leaving Iran under pressure following the Arab Muslim conquest and eventually settling on the western coast of India, at a place they named Sanjan after a town in their Iranian homeland. The traditional account places the migration in stages, first to the island of Hormuz in the Persian Gulf and then, after a period of years, onward to Gujarat, where local tradition holds that the migrants secured permission to settle from a Hindu ruler, Jadi Rana, after agreeing to conditions including adopting the local language and certain local customs while retaining their own religion.
The community that settled at Sanjan and its surrounding region became the ancestors of the Parsi community, whose name derives from Pars, the Iranian province of their origin. Over succeeding centuries, this community established fire temples, developed its own religious and social institutions adapted to an Indian setting, and gradually spread from its original settlement into other parts of western India, eventually concentrating heavily in Bombay from the early modern period onward.
The precise century of the initial migration is not fixed with confidence even within the traditional account itself, and modern historians generally place it somewhere within the eighth to tenth centuries CE, without being able to narrow the range further from currently available evidence.