Nibia was a planet with multiple moons.

In 2285, Khan, during his mission of vengeance against James Kirk, swore he would chase Kirk "'round the moons of Nibia and 'round the Antares maelstrom and 'round perdition's flames" before giving up. (Star Trek II: The Wrath of Khan)

This planet was only mentioned in dialogue.
According to the non-canon Star Trek: Ships of the Line (2015), one of the moons of Nibia was known to be a small, cratered world fortified by multiple large bases. Multiple Federation starships once waged an assault upon the moons of Nibia in the 24th century.