In Greek mythology, Echidna (/ɪˈkɪdnə/; Greek: Ἔχιδνα, "She-Viper") was a monster, half-woman and half-snake, who lived alone in a cave. She was the mate of the most fearsome monster Typhon. She was known primarily for being the mother of monsters, and many of the more famous monsters in Greek myth were said to be her offspring.
Echidna's family tree, varies by author. The oldest genealogy relating to Echidna is found in Hesiod's Theogony (c. 8th – 7th century BC), which is however unclear at several points. According to Hesiod, Echidna was born to a "she" who was probably meant by Hesiod to be the sea goddess Ceto, making Echidna's father (presumably) the sea god Phorcys, although the "she" might possibly refer instead to the naiad Callirhoe, which would make Chrysaor Echidna's father. Pherecydes of Leros (5th Century BC) has Echidna as the daughter of Phorkys, without naming a mother.
Other authors give Echidna other parents. According to Epimenides (as attributed by Pausanias), Echidna was the daughter of the Oceanid Styx (goddess of the river Styx) and one Peiras (otherwise unknown to Pausanias), while according to Apollodorus, Echidna was the daughter of Tartarus and Gaia. In one account, from the Orphic tradition, Echidna was the daughter of Phanes.
Hesiod's Echidna was half beautiful maiden (presumably the upper half) and half fearsome snake. Hesiod described "the goddess fierce Echidna" as a flesh eating "monster, irresistible", who was like neither "mortal men" nor "the undying gods", but was "half a nymph with glancing eyes and fair cheeks, and half again a huge snake, great and awful, with speckled skin", who "dies not nor grows old all her days." Hesiod's apparent association of the eating of raw flesh with Echidna's snake half, suggests that Hesiod may have supposed that Echidna's snake half ended in a snake-head. And Aristophanes, who makes Echidna a monster of the underworld, gives her a hundred heads (presumably snake heads), matching the hundred snake heads Hesiod says her mate Typhon had.
In the Orphic account (mentioned above) Echidna is described as having the head of a beautiful woman with long hair, and a serpent's body from the neck down. Nonnus, in his Dionysiaca, describes Echidna as being "hideous", with "horrible poison".