Amphitrite ("the third one who encircles (the sea))" was a sea goddess and the wife of Poseidon. Various versions of her say she was born to either Oceanus and Tethys, or Nereus and Doris. She was a sea nymph, a Halia, a personification of the sea itself.
Her sister Thetis was the original target of Poseidon's (and Zeus') wooing until a prophecy that she would bear a son greater than his father was made known to them. Thetis eventually married King Peleus of Iolcus and bore him Achilles.
On Greek amphorae, Amphitrite is usually placed with her consort while riding in a chariot pulled by sea creatures, or sitting on a sea creature of some kind. She is often decorated with the specific features of a queen; one shows her waving hair covered with a net, and sometimes with lobster pincers on her temples.
Her Roman equivalent is Salacia, the goddess of saltwater.
When Poseidon wanted Amphitrite as his bride after he saw her dancing on Naxos, she declined the great honour and hid from him in the Atlantic Ocean. A dolphin had found her and brought her back to Poseidon; the sea-god rewarded the dolphin with a place in the heavens, the constellation known as Delphinus. They were married and their son was Triton the first known 'merman' born with the tail of a fish and often depicted as blowing on a conch horn.