Nereus, in Greek religion, sea god called by Homer “Old Man of the Sea,” noted for his wisdom, gift of prophecy, and ability to change his shape. He was the son of Pontus, a personification of the sea, and Gaea, the Earth goddess. The Nereids (water nymphs) were his daughters by the Oceanid Doris, and he lived with them in the depths of the sea, particularly the Aegean. Aphrodite, the goddess of love, was his pupil. The Greek hero Heracles, in his quest for the golden apples of the Hesperides, obtained directions from Nereus by wrestling with him in his many forms. Nereus frequently appears in vase paintings as a dignified spectator.