Poseidon is the ancient Greek god of the sea, earthquakes, and horses. He is one of the twelve Olympian deities and is often depicted holding a trident, which symbolizes his power over the oceans. Poseidon was known for his volatile nature, capable of both creating calm seas and unleashing destructive storms. As the brother of Zeus and Hades, Poseidon played a crucial role in Greek mythology. He was worshipped by sailors and fishermen who sought his favor for safe voyages. His Roman counterpart is Neptune, and he is often associated with various myths involving sea creatures and underwater adventures.