Mithraism was a Roman mystery religion centered around the god Mithras, also referred to as the Mithraic mysteries. While the Roman version of Mithras was inspired by the Iranian worship of the Zoroastrian god Mithra, the iconography and practices associated with Roman Mithras diverged significantly from their Persian counterparts. The degree of continuity between Persian and Greco-Roman rituals is a subject of ongoing debate among scholars. Mithraism flourished from the 1st to the 4th century CE, particularly among the soldiers of the Roman Empire.

The worship of Mithras involved a complex system of initiation, with seven distinct levels that initiates progressed through. This initiation process was accompanied by ceremonial feasts, and those who joined the religion were called *syndexioi*, meaning "joined by the handshake." These initiates gathered in vast numbers within underground shrines known as *mithraea*. The religion likely originated in Rome, but its influence spread throughout the western Roman Empire, reaching as far as Roman Africa, Numidia, and Roman Britain. Mithraism also had a lesser presence in Roman Syria in the east, though it was never as widespread in that region.

In the early centuries of the Roman Empire, Mithraism and early Christianity were seen as competing religious systems, with Christians later persecuting Mithraists during the 4th century. Over time, Mithraism was gradually repressed and eventually eradicated from the Roman Empire by the end of the 4th century.