The Dionysian Mysteries were a ritual of ancient Greece and Rome which used intoxicants and other trance-inducing techniques (like dance and music) to remove inhibitions and social constraints, liberating the individual to return to a natural state. It also provided some liberation for those marginalized by Greek society: women, slaves and foreigners. In their final phase the Mysteries shifted their emphasis from a chthonic, underworld orientation to a transcendental, mystical one, with Dionysus changing his nature accordingly. By its nature as a mystery religion reserved for the initiated, many aspects of the Dionysian cult remain unknown and were lost with the decline of Greco-Roman polytheism; modern knowledge is derived from descriptions, imagery and cross-cultural studies.
The Dionysian Mysteries of mainland Greece and the Roman Empire are thought to have evolved from a more primitive initiatory cult of unknown origin (perhaps Thracian or Phrygian) which had spread throughout the Mediterranean region by the start of the Classical Greek period. Its spread was associated with the dissemination of wine, a sacrament or entheogen with which it appears always to have been closely associated (though mead may have been the original sacrament). Beginning as a simple rite, it evolved quickly within Greek culture into a popular mystery religion, which absorbed a variety of similar cults (and their gods) in a typically Greek synthesis across its territories; one late form was the Orphic Mysteries. However, all stages of this developmental spectrum appear to have continued in parallel throughout the eastern Mediterranean until late in Greek history and forcible Christianization.