The term Osiris-Dionysus is used by some historians of religion to refer to a group of deities worshipped around the Mediterranean in the centuries prior to the birth of Jesus. It has been argued that these deities were closely related and shared many characteristics, most notably dying and rising.

Ancient Syncretism

Osiris and Dionysus had been equated as long ago as the 5th century BC by the historian Herodotus (see interpretatio graeca). By Late Antiquity, some Gnostic and Neoplatonist thinkers had expanded this syncretic equation to include Aion , Adonis, Attis, Mithras and other gods of the mystery religions.

With the growth of Christianity, some pagan polemicists charged that the Gospels' narrative of Jesus's death and resurrection was in fact a bastardized reworking of the sufferings of Dionysus and other similar gods. Christian apologists like Justin Martyr charged in turn that the pagan mystery-cults were degenerate adaptations of Biblical prophecies about the Messiah. Jews like Philo of Alexandria also observed similarities and postulated that the pagan religions had borrowed from Jewish scriptures.

Modern Era

In the 19th century, the idea of a pan-Mediterranean cult of the dying-and-rising demigod was used by Alexander Hislop in his anti-Roman Catholic broadside The Two Babylons. Hislop argued that Roman Catholicism was based not upon Biblical Christianity, but upon pagan cults of the divine mother goddess and her suffering son (e.g. Cybele and Attis, etc.).

Later authors, such as Peter Gandy and Timothy Freke, have expanded this line of reasoning to encompass not merely Roman Catholicism, but Christianity more generally. Their book, The Jesus Mysteries, contends that Jesus was not an historical figure, but rather a mythic product of the same pan-Mediterranean mythic complex that also yielded Osiris, Dionysus and other similar figures.

Such arguments, however, have failed to win over many mainstream scholars. On the other hand, some academics do accept more limited pagan-to-Christian borrowings, such as iconographic characteristics of Orpheus and Mithras applied to Christ in early Christian art .