Thalassa (Greek: θάλασσα, Θάλλασση or Θάλαττη, "sea") was, in Greek myth, one of the earliest pre-Olympic female personifications of the Mediterranean Sea and, by extension, the entire ocean. She was the daughter of Aether with Hesperus.
With Pontos, she was the mother of all the fish and sea creatures, the nymph Halia, sometimes also the giant Egeon, the personification of the Aegean sea, and the nine Telquines.
When Uranus' semen fertilized her, she had Dione, the goddess of the nymphs. Another version places Dione as one of the Oceanids, and this same version places Thalassa as Aphrodite's mother with Uranus.