Neptune (Latin: Neptūnus) was the Roman god of water and the sea in Roman mythology and religion. He is the counterpart of the Greek god Poseidon. In the Greek-influenced tradition, Neptune was the brother of Jupiter and Pluto, each of them presiding over one of the three realms of Heaven, Earth and the Netherigions. Depictions of Neptune in Roman mosaics, especially those of North Africa, are influenced by Hellenistic conventions.
Neptune was likely associated with fresh water springs before the sea. Like Poseidon, Neptune was worshipped by the Romans also as a god of horses, under the name Neptunus Equester, a patron of horse-racing.