The Kingdom of Atlantis is a submerged kingdom located underneath the North Atlantic Ocean. It represents one of the earliest and most highly advanced cultural societies on Earth and also one of the most reclusive, actively avoiding and abhorring contact with the "surface world".
Untold millennia ago, groups of pilgrims settled in the greater Atlantean region establishing twelve distinctive communities, a few of which evolved into the city-states now known as Poseidonis and Tritonis.
Atlantis owed a lot of its development to the strong mystical energies intrinsically tied to the land. Over 145,000 years ago, two powerful mystics named Calculha and Majistra became the most powerful sorcerers in the world. Calculha, a follower of the light, manipulated White Magic, while his only living equal, the sorceress Majistra, was a practitioner of the dark arts. Through their influence, Atlantis flourished and grew into an advanced community unlike any other on the planet. Although magic was the dominant means of power throughout the continent, noted intellectuals began to recognize the wisdom of science. While the rest of the world had yet to benefit from inventions such as the wheel, the Atlanteans were already developing highly advanced technological wonders.
As the centuries passed, the sorcerers Calculha and Majistra decided to consolidate their mystical prowess and mate with one another. Their union produced twin offspring, Garn Daanuth and Arion. Calculha took Arion under his wing and apprenticed him in the arts of pure magic, while Majistra schooled Garn in the ways of evil. The children each grew up to become powerful mages in their own right, and the bitterest of enemies. Arion eventually defeated his brother, but at great cost to himself.
Some 9,600 years ago, a giant skull-shaped meteor crashed into the Earth somewhere near the North Sea. The impact caused a worldwide geological upheaval which became known as the Great Deluge (sometimes referred to as the Great Flood); tectonic plates shifted, yielding massive flooding so intense that it caused the entire continent of Atlantis to sink beneath the waves. Though nearly all of Atlantean culture had been wiped away forever, those of the capital city of Poseidonis managed to survive due to the erection of a giant dome, previously erected as a defence against barbarian tribes, that shielded the entire city.
While they had survived, the citizens of Poseidonis could no longer leave their city due to the depths surrounding them outside the dome. Shalako, brother to the city's monarch, King Orin, used his magic to protect his followers from the crushing pressure of the ocean depths, and they migrated from Poseidonis and re-established a colony in the ruins of the sister-city Tritonis.
A few short years after the calamity, Atlantis' monarch, King Orin, had his scientists develop a means so that his people could survive underwater, without having to stay within the city. The experiment was a success and the serum transformed the Atlanteans from normal human beings into aquatic amphibians who could survive the ocean depths and draw oxygen from water to breathe.
Meanwhile, due to Shalako's magic, the citizens of Tritonis evolved into a race of Mer-people with fins instead of legs. The most severe example of this effect was the Atlantean prince Kordax. Shalako's grandson Kordax was born a hideous, green-scaled mutant with blond hair and the ability to telepathically control the creatures of the sea. The existence of Kordax caused a schism throughout Atlantis as by right of ascension. This conflict erupted into a massive war between Poseidonis and Tritonis and led them in a revolution against the Poseidonian King. When the revolution failed, Kordax was exiled and children born with blonde hair, the "mark of Kordax", were generally viewed as aberrations and abandoned to die.
- During the Tides of War, Ocean Master incites a mutiny in an attempt to claim Aquaman's throne. As the battle between Atlantean and Mutineer frigates moves into the strait between Metropolis and Little Bohemia, Oracle instructs New Heroes to assist Aquaman in quelling the coup while Calculator shepards New Villains into supporting Ocean Master's mutiny.
- Circe in the form of Queen Mera has mesmerized Aquaman into leading his forces into attacking Metropolis
- Atlantis first appeared in Action Comics #18 (November 1939)
- A trio of clocks within the JSA Metropolis Wing reveals that Gotham City, Metropolis and Atlantis exist in different timezones.
- If it is taken that Metropolis is a stand-in for New York City, it would mean Atlantis is on the eastern edge of the Atlantic Ocean.
- Legend has it that the Atlanteans managed to combine science and sorcery to create the world's first space-craft. This vessel is thought to have left the planet Earth some 50,000 years ago. Some have speculated that the crew of this craft may have populated the nearby human worlds of Rann, Thanagar, and Krypton.
- Atlanteans can only exist outside of water for a limited period of time or else they will dehydrate, asphyxiate and ultimately die. A typical Atlantean can exist outside of water for around 2 hours before needing hydration; due to his enhanced biology, Aquaman can exist for around 24 hours before needing hydration.
- The "Curse of Kordax" is an omen that dates back to the time of ancient Atlantis when it was ruled by a tyrant known as Kordax. Because Kordax was distinguished by his blond hair and his ability to telepathically communicate with marine life, it was believed that any Atlantean born with blond hair would grow-up to become like Kordax and as such were effectively "disposed of".