Oceanus (Greek: Ὠκεανός) was a pseudo-geographical feature in classical antiquity, believed by the ancient Greeks and Romans to be the divine personification of the World Ocean, an enormous river encircling the world.
In Greek mythology, this world-ocean was personified as a Titan, a son of Uranus and Gaea. In Hellenistic mosaics, this Titan was often depicted as having the upper body of a muscular man with a long beard and horns (often represented as the claws of a crab) and the lower body of a serpent (cf. Typhon). On a fragmentary archaic vessel of circa 580 BC (British Museum 1971.11-1.1), among the gods arriving at the wedding of Peleus and the sea-nymph Thetis, is a fish-tailed Oceanus, with a fish in one hand and a serpent in the other, gifts of bounty and prophecy. In Roman mosaics, such as that from Bardo he might carry a steering-oar and cradle a ship.
Some scholars believe that Oceanus originally represented all bodies of salt water, including the Mediterranean Sea and the Atlantic Ocean, the two largest bodies known to the ancient Greeks. However, as geography became more accurate, Oceanus came to represent the stranger, more unknown waters of the Atlantic Ocean (also called the “Ocean Sea”), while the newcomer of a later generation, Poseidon, ruled over the Mediterranean.
Oceanus’ consort is his sister Tethys, and from their union came the ocean nymphs, also known as the three-thousand Oceanids, and all the rivers of the world, fountains, and lakes. From Cronus, of the race of Titans, the Olympian gods have their birth, and Hera mentions twice in Iliad book XIV her intended journey “to the ends of the generous earth on a visit to Oceanus, whence the gods have risen, and Tethys our mother who brought me up kindly in their own house.”
In most variations of the war between the Titans and the Olympians, or Titanomachy, Oceanus, along with Prometheus and Themis, did not take the side of his fellow Titans against the Olympians, but instead withdrew from the conflict. In most variations of this myth, Oceanus also refused to side with Cronus in the latter’s revolt against their father, Uranus.