The religion of the Greeks and Romans in the period before and after the invention of Christianity provides a special kind of foil to our understanding of modern world religions. Firstly, it provides the religious background against which Judaism, Christianity and eventually Islam first arose and it deeply influenced their development. Secondly, in the period before these religions developed, it provides us with a model of a sophisticated society that had no such autonomous religions at work in it at all. All too often books have been constructed on the assumption that religion was a marginal part of life, interesting perhaps in an antiquarian way, but scarcely needing to be placed at the centre of our understanding. But the fact is that religious activity formed part of every other activity in the ancient world; and so far from placing it in the margin of our accounts, it needs to be assessed at every point, in every transaction. This New Survey offers a picture of Roman religion and of some of the current debates about its character and development. The focus of the survey is the religious experience of the Roman people from about the third century BC to the second century AD. It does not attempt to discuss the establishment of Christianity as the main religion of the Empire in the fourth century; nor to do more than survey earlier theories about the earliest period of Rome as a city.