In Greek mythology, Eumolpus (also Eumolpos) was the son of Poseidon and Chione. According to the Bibliotheca, Chione, daughter of Boreas and Oreithyia, pregnant with Eumolpus by Poseidon, was frightened of her father's reaction so she threw the baby into the ocean. Poseidon looked after him and brought him to shore in Ethiopia, where Benthesikyme, a daughter of Poseidon and Amphitrite, raised the child, who then married one of Benthesikyme's two daughters by her Ethiopian husband. Eumolpus however loved a different daughter and was banished because of this. He went with his son Ismarus (or Immaradus) to Thrace. There, he was discovered in a plot to overthrow King Tegyrios and fled to Eleusis.
In Eleusis, Eumolpus became one of the first priests of Demeter and one of the founders of the Eleusinian Mysteries. He initiated Heracles into the mysteries. When Ismarus died, Tegyrios sent for Eumolpus, they made peace and Eumolpus inherited the Thracian kingdom. Eumolpus was an excellent musician and singer; he played the aulos and the lyre. He won a musical contest in the funereal games of Pelias. He taught music to Heracles. During a war between Athens and Eleusis, Eumolpus sided with Eleusis. His son, Himmarados, was killed by King Erechtheus. In some sources, Erechtheus also killed Eumolpus and that Poseidon asked Zeus to avenge his son's death. Zeus killed Erechtheus with a lightning bolt or Poseidon made the earth open up and swallow Erechtheus. Eleusis lost the battle with Athens but the Eumolpides and Kerykes, two families of priests to Demeter, continued the Eleusinian mysteries. Eumolpus' youngest son, Herald-Keryx founded the lines. According to Diogenes Laertius Eumolpus was the father of Musaeus.
- Apollodorus, 3.15.4 , Pausanias, 1.38.2
- Homeric Hymn to Demeter, 147 , 474
- Apollodorus, 2.5.12
- Apollodorus, 3.15.4
- Diogenes Laertius, Lives Introduction
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- Apollodorus, Apollodorus, The Library, Sir James George Frazer (translator), two volumes: Loeb Classical Library, #121, Books I-III and #122, Book III; Cambridge, MA, Harvard University Press; (1921) ISBN 0-674-99135-4, ISBN 0-674-99136-2
- Graves, Robert. The Greek Myths. Volume 1, Penguin Books, Revised Edition (1960), Reprinted 1986.
- Pausanias, Description of Greece, Books I-II, (Loeb Classical Library) translated by W. H. S. Jones; Cambridge, Massachusetts: Harvard University Press; London, William Heinemann Ltd. (1918) ISBN 0-674-99104-4