Neptune is the ancient Roman god of the sea, and Poseidon is the Greek god of the sea. They look similar in depictions, and some consider them to be the same god with two different names. Many people believe the Romans adopted the Greek god Poseidon and changed his name to Neptune.
Neptune was the brother of the god Pluto, the king of the underworld, and of Jupiter, the king of the gods. He was the son of Saturn and Rhea. He was described as having dark hair and a sea-green robe. He sat in a large shell pulled by seahorses and carried a trident.
Poseidon was one of the 12 Olympian gods. His parents were Cronus and Rhea. His brothers were Hades and Zeus, and his sisters were Demeter, Hera and Hestia. His wife was the sea goddess Amphitrite, and their children were Rhode and Triton. Poseidon is often pictured traveling in the water on his chariot and is considered a savior of ships as they cross the oceans. The Greeks believed he had supernatural powers over the sea. He carried a trident that caused earthquakes and tempests when he chose to use it. He was said to have a bad temper and used floods to exact revenge on those who did not do as he asked.