Neptune (海王星; Star of the Ocean's King) is the eighth planet from the Sun in this Solar System. It has 13 known moons, but the largest is Triton. It is grouped with Jupiter, Saturn, and Uranus as a planet of the outer Solar System.
In the Sailor Moon series, Neptune was protected by Sailor Neptune, even though in the present she resided on Earth with the other Sailor Senshi of the system. During the time of the Silver Millennium, Sailor Neptune remained there alone.
In the manga and Sailor Moon Crystal, Triton Castle orbited Neptune, and was the palace of Princess Neptune. The Sailor Crystal associated with her planet was the Neptune Crystal.
Neptune, also known as Poseidon in the Greek pantheon, was the god of water and the sea. He was the son of Saturn and Ops, and the brother of Jupiter and Pluto. Neptune was often associated with horses.
Neptune is associated with idealism, imagination, self-sacrifice, spirituality, creativity, sensitivity, and compassion.