Orthus was a two-headed dog, one of the fearsome children of Echidna and Typhoeus. He served as a guard dog to Geryon, a monster with three heads and three bodies who lived somewhere at the edge of the world. When Heracles came to steal Geryon’s cattle for his tenth labor, both Orthus and his master were killed while trying to defend the herd.
The name “Orthus” (Greek Ὄρθος, translit. Órthos) may be etymologically connected to the Greek noun ὄρθρος (órthros), meaning “daybreak, dawn”—a word that may itself have Indo-European origins. The name also resembles another Greek word, ὀρθός (orthós), meaning “straight, upright.”
Orthus lived with his master (and cousin) Geryon in “sea-girt” Erytheia, a mysterious land at the edge of the world. Most ancient writers placed it somewhere in Spain, in the neighborhood of modern Cadiz.
Orthus was typically said to have been a two-headed dog. But in artistic depictions (mostly on vase paintings), the number of heads varied between one and three. Sometimes he was also shown with a snake in place of a tail. In at least one tradition, Orthus was imagined as multiple guard dogs rather than a single multi-headed dog.
One late source added that he had seven dragon or snake heads in addition to the canine ones.
Orthus appeared only sporadically in ancient art, and only in connection with Heracles’ tenth labor (the theft of Geryon’s cattle). In those scenes, Orthus was usually shown lying dead, often with arrows protruding from his body.
Orthus was one of the terrifying children of the monsters Typhoeus and Echidna. His siblings included Cerberus, the three-headed guard dog of the Underworld, who was captured by Heracles; the Hydra, a many-headed serpent, who, like Orthus, was slain by Heracles; and (possibly) the Chimera, a fire-breathing creature with the features of a goat, a lion, and a snake, who was killed by Bellerophon.
Orthus’ only mythological role was in connection with Heracles’ famous Twelve Labors. For the tenth labor, Heracles had been commanded by Eursytheus, his taskmaster, to travel to Erytheia and bring back the splendid cattle of Geryon.
When Heracles reached Erytheia, he first had to face Geryon’s guard dog, Orthus, and his herdsman, Eurytion. But this did not detain him long. According to Apollodorus, Heracles killed Orthus with a single swing of his heavy club. When Geryon’s herdsman came to help, Heracles swiftly dispatched him, too.
Geryon finally armed himself and came out to meet the hero who was hell-bent on stealing his cattle. But Heracles killed him just as quickly—either with his club or, according to Apollodorus, with a single arrow.