A child of Typhon and Echidna, and brother to Cerberus. Orthrus was a two-headed, serpent-tailed dog who with the giant shepherd Eurytion guarded the oxen of Geryon. The dog was killed by Heracles when he stole Geryon's cattle as the tenth of his Twelve Labors.
- Hesiod. Theogony, 293, 309.
- Pseudo-Apollodorus. The Library ii, 5.10.