In Greek mythology

Greek mythology

Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

, Orthrus (Orthros) or Orthus (Orthos) was a two-headed dog

Dog

The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

 and a doublet ("brother") of Cerberus

Cerberus

Cerberus , or Kerberos, in Greek and Roman mythology, is a multi-headed hound which guards the gates of the Underworld, to prevent those who have crossed the river Styx from ever escaping...

, both whelped by the chthonic

Chthonic

Chthonic designates, or pertains to, deities or spirits of the underworld, especially in relation to Greek religion. The Greek word khthon is one of several for "earth"; it typically refers to the interior of the soil, rather than the living surface of the land or the land as territory...

 monsters Echidna

Echidna (mythology)

In Greek mythology, Echidna was half woman half snake, known as the "Mother of All Monsters" because most of the monsters in Greek myth were mothered by her...

 and Typhon

Typhon

Typhon , also Typhoeus , Typhaon or Typhos was the last son of Gaia, fathered by Tartarus, and the most deadly monster of Greek mythology. He was known as the "Father of all monsters"; his wife Echidna was likewise the "Mother of All Monsters."Typhon was described in pseudo-Apollodorus,...

.

He was owned by the three-bodied giant, Geryon

Geryon

In Greek mythology, Geryon , son of Chrysaor and Callirrhoe and grandson of Medusa, was a fearsome giant who dwelt on the island Erytheia of the mythic Hesperides in the far west of the Mediterranean. A more literal-minded later generation of Greeks associated the region with Tartessos in southern...

. Orthrus and his master, Eurytion

Eurytion

In Greek mythology Eurytion , "widely-honoured", was a name attributed to six individuals....

, were charged with guarding Geryon's herd of red cattle in the "sunset" land of Erytheia ("red one"), one of the islands of the Hesperides

Hesperides

In Greek mythology, the Hesperides are nymphs who tend a blissful garden in a far western corner of the world, located near the Atlas mountains in North Africa at the edge of the encircling Oceanus, the world-ocean....

 in the far west of the Mediterranean.