The underwater kingdom ruled by King Triton in Disney’s 1989 animated film The Little Mermaid is Atlantica.
Atlantica is the home of Ariel, her sisters, King Triton, Sebastian, and many other merfolk. The kingdom is presented through the opening musical number and scenes in Triton’s palace, where Ariel’s fascination with the human world conflicts with her father’s strict rules.
The name appears in Disney’s broader character and setting material and is commonly used for Triton’s underwater realm. The 1989 film focuses more on Ariel’s personal adventure than on political geography, so viewers may remember the palace and coral surroundings without recalling the kingdom’s name.
Atlantica should not be confused with Atlantis, the legendary city from other stories, or with locations invented for unrelated mermaid franchises. Disney’s Mermaid setting includes both an underwater royal kingdom and a separate human kingdom where Prince Eric lives.