Statue of Neptune, 2nd century AD, Prado Museum, Spain.
In Roman mythology, Neptune was the god of water and the sea. He was a relative of Ceres. His Greek equivalent is the god Poseidon. The Roman conception of Neptune was mainly influenced by the Etruscan god Nethuns.
Neptune was associated with fresh water as well as the sea, Oceanus was the god of the world-ocean.
Like Poseidon, Neptune was also worshiped by the Romans as the god of horses, under the name Neptune Equester, he was a patron of horse-racing.