Neptune's presence in Marvel Comics has two distinct starting points, reflecting the company's evolution from Timely Comics to the modern Marvel era. An early, prototypical version of the character (or a being using his name) first appeared in the Golden Age in Kid Komics #1 in February 1943, in a story titled “The Sub-Earthmen.” However, this incarnation bears little resemblance to the character known today. The definitive, modern version of Neptune, who would become a fixture of the Marvel Universe, was introduced during the Silver Age. He made his official debut in Tales to Astonish #70, published in August 1965. This introduction was helmed by the legendary creative duo of writer Stan Lee and artist Jack Kirby. His creation was part of Lee and Kirby's grand strategy of weaving mythological pantheons into the fabric of their superhero universe, a successful endeavor that had already brought the Norse gods, including Thor and Odin, to prominence. By introducing the Greek and Roman gods, they created a new pantheon of cosmic beings to act as allies, antagonists, and a source of epic, world-shaking stories, firmly establishing that Earth-616 was a stage for gods as well as heroes.
The in-universe origins of Neptune are steeped in cosmic antiquity and divine warfare, with a clear separation between the established comic canon and the cinematic universe's complete divergence.
Neptune is a member of the Olympians, a race of extra-dimensional beings of immense power who were worshipped as gods by the ancient Greeks and Romans.1) He is the son of the Titans Cronus and Rhea, two of the original elder gods who ruled the Earth dimension. Cronus, fearing a prophecy that he would be overthrown by his own children, devoured each of them at birth. Neptune, along with his siblings Hades (Pluto), Hera, Hestia, and Demeter, were consumed. His youngest brother, Zeus, was spared this fate by Rhea's trickery and was raised in secret. Upon reaching adulthood, Zeus returned and forced Cronus to regurgitate his siblings, who had matured into powerful adult gods while imprisoned. This act of liberation sparked the Titanomachy, a cataclysmic ten-year war between the new generation of Olympian gods and the ruling Titans. Neptune fought valiantly alongside his brothers and sisters. With the aid of the Cyclopes, who forged legendary weapons for them, the Olympians were victorious. They received the lightning bolts for Zeus, the Helm of Darkness for Pluto, and a mighty Trident for Neptune. Following their victory, the three brothers cast lots to divide the cosmos. Zeus claimed dominion over the heavens and became the Sky-Father and King of the Olympians. Pluto claimed the Underworld, becoming the god of the dead. Neptune was granted sovereignty over all of Earth's seas and oceans. He established his own aquatic kingdom, the dimension of Elysium, a separate realm connected to Earth's oceans, and took the sea-goddess Amphitrite as his queen and the merman-like god Triton as his son. For millennia, Neptune ruled his domain, interacting with mortals primarily through worship and myth. His most critical modern-era connection came through the Atlanteans. The ancient Atlanteans revered Neptune (as Poseidon), and in a pivotal moment of their history, he sired a child with an Atlantean woman. This act infused his divine bloodline into the Atlantean royal family, a lineage that would eventually produce Princess Fen, the mother of Namor the Sub-Mariner. This makes Neptune the great-grandfather of Namor, a fact that has been used to both test and empower the Atlantean king throughout his long life.
Neptune, the Olympian pantheon, and the Greco-Roman version of Atlantis do not exist in the Marvel Cinematic Universe as of current storytelling. The MCU's narrative took a radically different and culturally specific approach to its