The cult of Mithras, usually called Mithraism, spread widely across the Roman world between the first and fourth centuries CE. Its origins, development, and relationship to earlier Iranian traditions remain subjects of scholarly debate. What we can study with greater certainty is the archaeological evidence left by its communities: temples, inscriptions, reliefs, altars, and objects associated with ritual activity. Yet Mithraea were more than simply places of worship. Their architecture, imagery, and archaeological contexts allow us to ask broader questions about religious identity, social networks, ritual practice, and the movement of ideas across the Empire. In this presentation, we will explore Mithras through the evidence of Rome and Ostia, moving from the enigmatic figure at the centre of the cult to the spaces, communities, and rituals that brought his worship to life.