Neptune was the Roman god who ruled the seas and was equivalent to the Greek Poseidon.
Neptune governed the sea and freshwater in Roman religion. In earlier Italian tradition, he may have been more closely connected with springs and inland waters before Roman theology adopted the powerful sea-god profile associated with Poseidon. He was also linked with horses, an attribute he shared with his Greek counterpart.
In the Greek-inspired Roman family tree, Neptune was the brother of Jupiter and Pluto. The three presided over the sky, the seas, and the underworld respectively. Neptune’s wife was Salacia, a goddess associated with salt water, and his familiar symbols included the trident, dolphin, horse, and marine chariot.
His major festival, the Neptunalia, was probably held on July 23, during the hottest and driest part of the Roman summer. Participants reportedly built leafy shelters and celebrated outdoors, emphasizing the value of water during drought. Romans sometimes treated Neptune as simply the Roman name for Poseidon, but his older freshwater associations show that the identification developed over time rather than being completely original.