The Old Man of the Sea was a primordial deity in Greek mythology, and was the personification of the sea. He was identified as one of various sea deities, such as Nereus, Proteus, Pontus, and Phorcys. He had a daughter, Thetis, the mother of the hero Achilles.
He appeared in the Homeric poem Odyssey, when Menelaus had to find him to get advice for how to return home. The Old Man of the Sea was able to change form and thus, it was difficult to be captured; Menelaus eventually captured him and asked him various questions for how to go back home.