Dionysus is the god of the grape harvest, winemaking and wine, of ritual madness, fertility, theatre and religious ecstasy in ancient Greek religion and myth. Wine played an important role in Greek culture, and the cult of Dionysus was the main religious focus for its unrestrained consumption. He may have been worshipped as early as c. 1500–1100 BC by Mycenean Greeks ; traces of Dionysian-type cult have also been found in ancient Minoan Crete. His origins are uncertain, and his cults took many forms; some are described by ancient sources as Thracian, others as Greek. In some cults, he arrives from the east, as an Asiatic foreigner; in others, from Ethiopia in the South. He is a god of epiphany, "the god that comes", and his "foreignness" as an arriving outsider-god may be inherent and essential to his cults. He is a major, popular figure of Greek Mythology and religion, becoming increasingly important over time, and included in some lists of the twelve olympians, as the last of their number, and the only god born from a mortal mother. His festivals were the driving force behind the development of Greek teatre.

The earliest cult images of Dionysus show a mature male, bearded and robed. He holds a fennel staff, tipped with a pine-cone and known as a thyrsus. Later images show him as a beardless, sensuous, naked or half-naked androgynous youth: the literature describes him as womanly or "man-womanish". In its fully developed form, his central cult imagery shows his triumphant, disorderly arrival or return, as if from some place beyond the borders of the known and civilized. His procession (thiasus) is made up of wild female followers (maenads) and bearded satyrs with erect penises; some are armed with the thyrsus, some dance or play music. The god himself is drawn in a chariot, usually by exotic beasts such as lions or tigers, and is sometimes attended by a bearded, drunken Silenus. This procession is presumed to be the cult model for the followers of his Dionysus Mysteries. Dionysus is represented by city religions as the protector of those who do not belong to conventional society and he thus symbolizes the chaotic, dangerous and unexpected, everything which escapes human reason and which can only be attributed to the unforeseeable action of the gods.