In Greek mythology, the Roman name for Poseidon, the Olympian god of the sea, was Neptune.
Poseidon was one of the three major sons of Cronus and Rhea, alongside Zeus and Hades. After the defeat of the Titans, the brothers divided the cosmos by lot: Zeus received the sky, Poseidon the sea, and Hades the underworld. Poseidon also ruled earthquakes and horses.
The Romans identified Poseidon with their own god Neptune, although Neptune originally had a more limited role in Roman religion and was not initially as strongly associated with the sea. Over time, Greek influence shaped Neptune into the Roman equivalent of Poseidon.
Poseidon is commonly confused with Neptune because the names belong to different mythological traditions. Neptune’s usual symbol was the trident, also associated with Poseidon, and both gods were linked to horses and water. Mars corresponds to Ares, Vulcan to Hephaestus, and Mercury to Hermes.