Oceanus was the oldest of all titans. He was the perfect river and the ruler of the waters and the seas. Oceanus was, according to Homer, the origin of all things and of all deities.

Oceanus was born out of Mother Earth Gaea and Uranus, the ruler of the heaven, when Uranus watered Gaea with divine rain. Oceanus formed a union with titaness Tethys and they created 3000 daughters, and gave them the name "Oceanids".

The main Oceanids were Styx, who personified the sacred river of the Underworld, Amphitrite, the future wife of Poseidon and Metis, the deity who bore inside herself all the wisdom of the world. Metis was the first wife of Zeus, the king of the gods, and mother of Athena, the Olympian goddess of Wisdom and War.