The origin story that results in Zeus exterminating Cronos and naming the gods to their corresponding realms is upheld by Homer and Hesiod in their writings. In the Mycenae region, there is thought that Poseidon was not originally connected to water or the seas. In a similar myth from Minoa, the goddess Pasiphae mates with a white bull (considered the pre-Olympian Poseidon) and gives birth to the Minotaur. This representation is common in norther-European folklore as well. There is some speculation that only a few gods were brought in by the Greeks, of which Poseidon was not one and initially he appears in the mythology as a horse representing the river spirit of the underworld. The emergence of Poseidon’s origin story is likely related to the first Greek speaking people who enter the Arcadian region during the Bronze Age, who mixed their religious beliefs with the local indigenous population. Cronus ate all of their children at birth until Rhea tricked him into eating a large rock rather than their sixth child, Zeus, which forced him to throw up all of the other children from which the Greek pantheon began to develop. Poseidon was born of the gods Cronus (Kronos) and Rhea. Much as with their roles as gods, the origin story of Poseidon and Neptune are quite similar.
![neptune poseidon neptune poseidon](https://i.etsystatic.com/14235498/r/il/70b737/1810286984/il_794xN.1810286984_b80j.jpg)
In Greece, it was Poseidon, Zeus and Hades. In Rome, this was Neptune, Jupiter and Pluto. Both structures had a god of the sea, a god of the sky and a god of the underworld. This would be an issue of semantics, and there are many commonalities in both the Greek god and the Roman god mythology to suggest their equivalence. Essentially, Poseidon is the Greek Neptune and Neptune is the Roman Poseidon.
![neptune poseidon neptune poseidon](https://www.jamesjchoi.com/images/Poseidon_Wetclay.jpg)
The primary reason that Poseidon and Neptune are considered the same god is because some think that they actually are. However, even if they are referencing the same god, their depictions are different in several key aspects (despite the fact that in art they frequently look very similar). Many believe that the Romans simply adopted the Greek god Poseidon and changed his name to Neptune. And indeed, they are both sea gods, however, whether or not they are the same god is up for debate. When hearing the names Neptune or Poseidon, many people conjure up the same image, that of a sea or water god and the horses, and always with a trident.