in Greek mythology, the river that flowed around the Earth (conceived as flat), for example, in the shield of Achilles described in Homer's Iliad, Book XVIII. Beyond it, to the west, were the sunless land of the Cimmerii, the country of dreams, and the entrance to the underworld. In Hesiod's Theogony, Oceanus was the oldest Titan, the son of Uranus (Heaven) and Gaea (Earth), the husband of the Titan Tethys, and father of 3,000 stream spirits and 3,000 ocean nymphs. In the Iliad, Book XIV, Oceanus is identified once as the begetter of the gods and once as the begetter of all things; although the comments were isolated, they were influential in later thinking. Oceanus also appears in Aeschylus's Prometheus Bound.

In art Oceanus was a common subject; he appears on the François Vase (see Kleitias), the Gigantomachy of the altar at Pergamum, and numerous Roman sarcophagi. As a common noun, the word received almost the modern sense of ocean.