Certain universal and more or less perennial aspects of human perceptions of the night influence the representation of nightlife in ancient texts. But beyond the stereotypes, we may recognize tensions between conservative perceptions and a continually changing reality. In the Roman empire, we may observe certain recurring elements of a ‘nocturnal koine’, the result of general trends. The factors that shaped nightlife in the Roman empire include the diffusion of voluntary associations and their convivial activities, the donations of benefactors for nighttime activities (baths, gymnasia, public banquets), the prominent place of nocturnal rites in cults with a soteriological or initiatory aspect, and efforts to increase the safety in cities during the night. These factors should be considered within a broader context—that of the gradual and continuous colonization of the night with the activities of the day.