Whereas toleration and intolerance are often studied for more recent periods of history, there is little scholarship on toleration in Classical Antiquity. This is due to the widespread assumption that Greco-Roman religions were essentially tolerant and that intolerance set in with the rise of Christianity. Alternatively, it is argued that toleration is a modern concept without emic equivalent in Antiquity and hence that there is no subject matter to study for the ancient world. Both views are indebted to the Enlightenment narrative according to which history is marked by a progress towards toleration in modern Europe. This project seeks to revitalize the study of toleration by putting it on a new footing. It first introduces a concept of toleration that understands it as a social practice for dealing with religious difference and deviance. Applying this conception to the ancient world, the project then proposes to study practices of, attitudes towards, and justifications of tolerance and intolerance through a series of casestudies with the aim of generating a much more nuanced image of how Greek and Roman societies dealt with religious difference. This will, finally, lead to revisions of the current idealizations of Greece and Rome in the broader history of toleration.