Poseidon was best-known as the Greek god of the sea. He was also the god of earthquakes and the god of horses. So, if you are asking his domain with respect to where he lived, that would be in the ocean or on the ocean floor, although the primary gods also had residences on Olympus. If you are asking his domain with respect to what he ruled over as a god, that would be the sea, earthquakes, and horses.
Poseidon is the god of earthquakes. No goddess has this responsibility.
The goddess Athena
Poseidon is King of the Sea. No god or goddess ruled him in his domain.
if this is what ur asking poseidon's wife amphitrite queen of the sea.
There is an older god of the sea: Nereus, who was replaced by the Olympian god, Poseidon. So there is no goddess of the sea. Amphitrite is the wife of Poseidon. She is then the sea goddess.
Amphitrite was the goddess of the sea, married to Poseidon, god of the sea
Poseidon
Poseidon
Kharybdis is sometimes told to be the daughter of Poseidon and Gaea. Antaeus was thier son, and Laistrygon who founded a tribe of man eating giants. By the earth goddess Demeter, Poseidon had the immortal horse Arion and the Mysteries goddess Despoena.
Poseidon had a favorite city, Athens. As you may have guested Athens is the Greek goddess' Athena, goddess of wisdom. Poseidon and Athena fought for Athens but, in the end Zeus gave it to Athena.
Poseidon is similar to the Roman god Neptune.
Athena, goddess of wisdom and war.