Iacchus was a minor deity connected with the Eleusinian Mysteries. He seems to be the personification of the ritual cry “Iacche!” exclaimed by the initiates during the grand procession from Athens to Eleusis. As such, he does not have notable mythology. In art, he is usually depicted as a young man holding torches in the presence of Demeter and Persephone. His statue was kept in a temple in Athens near the Dipylon gate in the Kerameikos district. According to Pausanias, the figure was made by Praxiteles. The artist depicted the young god holding a torch and wearing a myrtle crown. On 19 Boedromion, the priests collected the statue and placed it at the head of the procession leading the sacred objects of Demeter and the initiates to Eleusis. There was a special Eleusinian official called Ιακχαγωγός, who was responsible for escorting or transporting the statue during the procession. Despite his prominent role in the procession, Iacchus vanished from the celebration of the Mysteries when the initiates arrived in Eleusis. Herodotus narrates the story of Iacchus appearing at the head of a massive assembly of thirty thousand men who seemed to march against the Persian army ravaging the Thriasian Plain on the eve of the battle of Salamis in 480 BCE. 

In some mythological traditions, Iacchus is the companion of Baubo when she attempts to entertain Demeter by lascivious gestures. According to the Orphics, Iacchus was identified with Dysaules and Eubouleus, two Eleusinian heroes or demi-gods. He also had a female aspect known as Misa, the “ineffable, pure, sacred queen, twofold Iakkhos, male and female”. The Orphics equated these aspects with Phanes, the primaeval deity of procreation. The Orphics also believed that Iacchus was the son of Persephone. Generally speaking, it seems like Iacchus was a minor deity whose worship was introduced to Athens by private individuals. They formed a religious association to organise Iacchus’ cult ritual. When Pisistratus decided to enlarge the Eleusinian Mysteries, the cult of Iacchus was incorporated into the more fabulous celebration, and his statue assumed its prominent position at the head of the grand procession. Interestingly enough, there never seems to have been a temple or a sanctuary dedicated to him in Eleusis.