According to the tradition in Apollodorus (iii. 15. § 4), Chione, after having given birth to Eumolpus in secret, threw the child into the sea. Poseidon, however, took him up, and had him educated in Ethiopia by his daughter Benthesicyma.
When he had grown up, he married a daughter of Benthesicyma but as he made an attempt upon the chastity of his wife's sister, Eumolpus and his son Ismarus were expelled, and they went to the Thracian king Tegyrius, who gave his daughter in marriage to Ismarus; but as Eumolpus drew upon himself the suspicion of Tegyrius he was again obliged to take to flight, and came to Eleusis in Attica, where he formed a friendship with the Eleusinians.
After the death of his son Ismarus, however, he returned to Thrace at the request of king, Tegyrius. The Eleusinians, who were involved in a war with Athens, called Eumolpus to their assistance. Eumolpus came with a numerous band of Thracians, but he was slain by Erechtheus.
The traditions about this Eleusinian war, however, differ very much. According to some, the Eleusinians under Eumolpus attacked the Athenians under Erechtheus, but were defeated, and Eumolpus with his two sons, Phorbas and Immaradus, were slain.
Pausanias (i. 38. § 3) relates a tradition that in the battle between the Eleusinians and Athenians, Erechtheus and Immaradus fell, and that thereupon peace was concluded on condition that the Eleusinians should in other respects be subject to Athens, but that they alone should have the celebration of their mysteries, and that Eumolpus and the daughters of Celeus should perform the customary sacrifices.
When Eumolpus died, his younger son Ceryx succeeded him in the priestly office. According to Hyginus Eumolpus came to Attica with a colony of Thracians, to claim the country as the property of his father, Poseidon.
Mythology regards Eumolpus as the founder of the Eleusinian mysteries, and as the first priest of Demeter and Dionysus; the goddess herself taught him, Triptolemus, Diocles, and Celeus, the sacred rites, and he is therefore sometimes described as having himself invented the cultivation of the vine and of fruit-trees in general.
As Eumolpus was regarded as an ancient priestly bard, poems and writings on the mysteries were fabricated and circulated at a later time under his name. One hexameter line of a Dionysiac hymn, ascribed to him, is preserved in Diodorus.
The legends connected him also with Heracles, whom he is said to have instructed in music, or initiated into the mysteries.
The difference in the traditions about Eumolpus led some of the ancients to suppose that two or three persons of that name ought to be distinguished.
The tomb of Eumolpus was shewn both at Eleusis and