This article is about the Greek sea goddess. For the sea monster, see Cetus.

Ceto, also Keto, Crataeis or Trienus was a Greek goddess of the sea, and the daughter of Gaia and Pontus. Her name is the feminine of Ketos/Cetus, which means "sea-monster". She was married to her brother Phorcys, with whom she conceived a slew of monstrous offspring. Her children are Echidna, the Gorgons, the Graeae, Scylla, Thoosa and Ladon. Her other siblings are Thaumas, Nereus and Eurybia.

Ceto (left) with her father Pontus (centre)