A late Mystery Religion supposedly derived from the Dionysian Mysteries. Scholars differ on whether an organised Mystery School really existed or whether this is merely a term for a set of late Greek belief's of Oriental influence that share a family resemblance. Also known as Orphism. But it seems likely some body of teaching existed and that those following it worshiped a refined form of Dionysos.
Like the early Dionysians Orphic mystics were nomadic and anarchic. They differed in being strict pacifists and vegetarians who followed a puritanical moral code. As ascetics they rejected the world, their motto being Soma Sema, 'the world a tomb'. They saw the material world as ruled by Titanic forces (the Titans), who had dismembered the unity of Dionysos and cast his fragments into gross matter forming Man. These divine sparks had to be released back into their source. They did however retain a bacchanalian orgiastic tradition, though this was for cathartic reasons and aimed at purification and the transcendence of desire. In many ways they parallel similar changes in the cult of Shiva in India, for them Dionysos is a chaotic but transcendental being, who is balenced by another lower transcendental being, Apollo, a benign demiurge, who adds order and harmony to the more primal Dionysian foundation. They also share many beliefs with Buddhism (such as reincarnation, detachment, the escape from the 'wheel of life' and a heavenly paradise for the enlightened).
It is believed they emerged from some catastrophic moral reversal which affected many Dionysians at some stage (though by no means all). Their origin is dated to around 500BC, though some scholars think they are later. They particularly emphasised and exaggerated notions about the afterlife prevalent in the Dionysian Mysteries.
A body of complex dogmatic teaching was associated with them which included cosmology, astrology, alchemy and magic. Many Greek Philosophers were influenced by their notions. Pythagoreanism was said to be a reform of Orphism by Pythagoras and Platonism a development of Pythagoreanism.
A body of Pythagorean Orphic Geomancers applied their beliefs to architecture and became known as the Dionysian Artificers. Legend has it these helped build Solomon's Temple, and are regarded as ancestors by some modern Freemasons.
The Orphic Mysteries shared an incredible number of similarities with Christianity, including baptism, a tradition of magical healing, a similar range of miracles attributed to a Christ-like Dionysos or his incarnations,
the concept of sin and the crucifixion of a scapegoat.
They could also be seen as the precursor of Gnosticism which was probably a descendent of Orphism.