In Greek mythology, the Old Man of the Sea was a figure who could be identified as any of several water-gods, generally Nereus or Proteus, but also Triton, Pontus, Phorcys or Glaucus. He is the father of Thetis.

In Greek mythology, Nereus was the eldest son of Pontus and Gaia, with Pontus himself being a son of Gaia. Nereus and Doris became the parents of 50 daughters and a son (Nerites), with whom Nereus lived in the Aegean Sea.