Oceanus or Okeanos, in the Greek mythology the great world-stream which surrounds the whole earth, and is the parent source of all seas and streams, presided over by a Titan, the husband of Tethys, and the father of all river-gods and water-nymphs. He is the all-father of the world, as his wife is the all-mother, and the pair occupy a palace apart on the extreme verge of the world.