In Greek mythology, Echidna (Ancient Greek: Ἔχιδνα, "she viper") was half woman half snake, known as the "Mother of All Monsters" because most of the monsters in Greek myth were mothered by her. Hesiod's Theogony described her as:
[...] the goddess fierce Echidna who is half a nymph with glancing eyes and fair cheeks, and half again a huge snake, great and awful, with speckled skin, eating raw flesh beneath the secret parts of the holy earth. And there she has a cave deep down under a hollow rock far from the deathless gods and mortal men. There, then, did the gods appoint her a glorious house to dwell in: and she keeps guard in Arima beneath the earth, grim Echidna, a nymph who dies not nor grows old all her days.
According to Apollodorus, Echidna was the daughter of Tartarus and Gaia, while according to Hesiod, either Ceto and Phorcys or Chrysaor and the naiad Callirhoe were her parents. Another account says her parents were Peiras and Styx (according to Pausanias, who did not know who Peiras was aside from her father). Echidna was a drakaina, with the face and torso of a beautiful woman (depicted as winged in archaic vase-paintings) and the body of a serpent, sometimes having two serpent's tails. She is also sometimes described, as Karl Kerenyi noted, in archaic vase-painting, with a pair of echidnas performing sacred rites in a vineyard, while on the opposite side of the vessel, goats were attacking the vines: thus chthonic Echidnae are presented as protectors of the vineyard.
The site of her cave Homer calls "Arima, couch of Typhoeus". When she and her mate attacked the Olympians, Zeus beat them back and punished Typhon by sealing him under Mount Etna. However, Zeus allowed Echidna and her children to live as a challenge to future heroes. Although to Hesiod, she was an immortal and ageless nymph, according to Apollodorus, Echidna used to "carry off passers-by", until she was finally killed where she slept by Argus Panoptes, the hundred-eyed giant.
Echidna was the mother by Typhon of many monstrous offspring, including:
- Orthrus - The two-headed dog which guarded the Cattle of Geryon.
- Cerberus - The many-headed dog which guarded the gates of Hades.
- The Lernaean Hydra - The many-headed serpent which when one of its heads was cut off grew two more.
- The Chimera - A fire breathing beast that was part lion, part goat, and had a snake-headed tail.
- The Caucasian Eagle — An eagle that every day ate the liver of Prometheus.
- The Crommyonian Sow - Killed by Theseus.
- The Gorgon - According to Hyginus.
- The Colchian Dragon - A dragon that guarded the Golden Fleece.
- Scylla - According to Hyginus.
- The Teumessian fox - A fox that was destined never to be caught. It was sometimes called the Cadmean vixen.
Also included as the offspring of Echidna by Typhon, by some, are the Sphinx and the Nemean lion. However Hesiod's genealogy here is unclear, he says these two were fathered by Orthrus, but he has been read variously as saying that Echidna, the Chimaera, or even Ceto, was their mother.
Ladon, the dragon which guarded the golden apples in the Garden of the Hesperides, was also born of Echidna by Typhon, according to Apollodorus, and Hyginus, but according to Hesiod, Ladon was the offspring of Ceto and Phorcys.
See also 
- Echidna, a monotreme mammal of Australia and New Guinea named after the mythological monster.
- Nāgas, water-dwelling beings of Hindu Mythology who are also half-serpent.
- Spenser's Errour in The Faerie Queene resembles Echidna in this hybrid nature, as John M. Steadman notes, in "Sin, Echidna and the Viper's Brood", The Modern Language Review 56.1 (January 1961:62-66) p. 62.
- Hesiod, Theogony 295-305.
- Apollodorus, Library 2.1.2
- Hesiod, Theogony 270-305. This passage has been read variously as saying that Ceto (Grimal, p. 143; Caldwell, p. 46) or Callirhoe (Morford, p. 162; Smith "Echidna") was the mother of Echidna. Athanassakis, p. 44, says that Phorcys and Ceto are the "more likely candidates for parents of this hideous creature who proceeded to give birth to a series of monsters and scourges ..." Herbert Jennings Rose says that it is "not clear which parents are meant". However, according to Clay, p. 159, note 32, "the modern scholarly consensus ... assigns the role to Keto".
- Pausanias, Description of Greece 8.18.2
- Lamia and other drakainas also combine human and serpentlike natures.
- Kerenyi, pp. 51–52
- Homer, Iliad 2.783
- Hesiod, Theogony 304
- Apollodorus, Library 2.5.10
- Hyginus, Fabulae Preface, 151
- Apollodorus, Library 2.3.1
- Apollodorus, Library 2.5.11
- Apollodorus, Epitome 1
- Apollodorus, Library 3.5.8
- Apollodorus, Library 2.5.1
- The problem arises from the ambiguous referent of the pronoun "she" in line 326 of the Theogony, see Clay, p.159, note 34
- Hesiod, Theogony 333–336
- Grimal, "Scythes" pp. 414–415.
- Apollodorus, Apollodorus, The Library, with an English Translation by Sir James George Frazer, F.B.A., F.R.S. in 2 Volumes, Cambridge, MA, Harvard University Press; London, William Heinemann Ltd. 1921
- Athanassakis, Apostolos N, Hesiod, Theogony ; Works and days ; Shield, JHU Press, 2004. ISBN 978-0-8018-7984-5.
- Caldwell, Richard, Hesiod's Theogony, Focus Publishing/R. Pullins Company (June 1, 1987). ISBN 978-0-941051-00-2.
- Clay, Jenny Strauss, Hesiod's Cosmos, Cambridge University Press, 2003. ISBN 978-0-521-82392-0.
- Grimal, Pierre, The Dictionary of Classical Mythology, Wiley-Blackwell, 1996, ISBN 978-0-631-20102-1. "Echidna" p. 143
- Hesiod, The Homeric Hymns and Homerica with an English Translation by Hugh G. Evelyn-White. Theogony, Cambridge, MA.,Harvard University Press; London, William Heinemann Ltd. 1914.
- Homer, The Iliad with an English Translation by A.T. Murray, Ph.D. in two volumes, Cambridge, MA., Harvard University Press; London, William Heinemann, Ltd. 1924.
- Hyginus, Gaius Julius, The Myths of Hyginus. Edited and translated by Mary A. Grant, Lawrence: University of Kansas Press, 1960.
- Kerenyi, Karl, The Gods of the Greeks, Thames and Hudson, London, 1951.
- Morford, Mark P. O., Robert J. Lenardon, Classical Mythology, Eighth Edition, Oxford University Press, 2007. ISBN 978-0-19-530805-1.
- Pausanias, Pausanias Description of Greece with an English Translation by W.H.S. Jones, Litt.D., and H.A. Ormerod, M.A., in 4 Volumes, Cambridge, MA, Harvard University Press; London, William Heinemann Ltd. 1918.
- Rose, Herbert Jennings, "Echidna" in The Oxford Classical Dictionary, Hammond and Scullard (editors), Second Edition, Oxford University Press, 1992. ISBN 0-19-869117-3
- Smith, William; Dictionary of Greek and Roman Biography and Mythology, London (1873). "Echidna"