Montanus was a Christian prophet from the region of Phrygia in Asia Minor during the second century CE. According to church historians, he began his prophetic activity sometime between 156 and 172 CE, shortly after converting to Christianity. His movement, originally called the New Prophecy and later known as Montanism, also featured two prominent female prophets, Priscilla and Maximilla. The movement spread from its rural origins to other parts of the Roman Empire, including North Africa.

Montanus and his followers believed they were direct vessels for the Holy Spirit, receiving new revelations that they felt completed the apostolic tradition. This placed them in conflict with the developing mainstream church, which relied on episcopal authority and apostolic succession. Church councils in Asia Minor condemned the movement as heretical. Accounts from opponents claim Montanus and Maximilla died by suicide, but these reports are considered unreliable and polemical.

No complete writings or treatises by Montanus himself survive. The movement produced a collection of prophetic sayings, or oracles, attributed to him and his fellow prophets, but these are known only through quotations by their critics, such as the historians Eusebius and Epiphanius.

Modern scholars interpret Montanism as a significant early Christian movement that emphasized ongoing prophecy, strict asceticism, and the imminent end of the world. The controversy it sparked helped accelerate the early church's efforts to define orthodox belief, establish the boundaries of the biblical canon, and formalize structures of authority. Although condemned, Montanism persisted for centuries and its emphasis on direct spiritual experience influenced later Christian ascetic and millenarian groups.