Religion has played an important rôle in man’s life, since times immemorial. A number of religious systems had their origin in ancient India, and she played host to a number of religious systems, which had their origins in other countries. The present work begins with religious life, beliefs, and philosophy, of the Harappan and vedic peoples, and goes on to deal with the heterodox sects—Jainism, Buddhism, Ājīvikism, and the doctrines of some other heretical teachers, and epic-puranic sects—Vaishṇavism, Śaivism, Śāktism, and other sects and religious denominations. The last four chapters are dedicated to religious systems, from ‘across the borders’ of India—Zoroastrianism, Greek religion, Christianity, and Islam, which have been discussed, in some detail. The numismatic evidence, for the worship of certain Roman and Alexandrian deities, and Oriental deities, has been briefly presented, under two separate appendices. These are usually missing in books, dealing with religious history in ancient India, although they were, very much, a part of the religious life of ancient Indians.