Orthrus or Orthus was a monster in Greek mythology, a dog with two heads and brother of Cerberus, the three-headed dog that guarded the Underworld. They were the offspring of the father and mother of all monsters, Typhoeus and Echidna respectively.
Orthrus was the dog of the giant Geryon, a three-bodied, three-headed creature that owned cattle in the land of Erytheia. Both Orthrus and Geryon were slain by the demigod hero Heracles, when he was asked to fetch the cattle of Geryon for Eurystheus, during the Labours of Heracles.
Orthrus Is also called Orthus.