Sailor Pluto (セーラープルート, Sērā Purūto) is a fictional character in the Sailor Moon manga series written by Naoko Takeuchi. The alternate identity of Setsuna Meiou (冥王 せつな, Meiō Setsuna, renamed "Trista Meioh" in some English adaptations), she is a member of the Sailor Guardians, female supernatural fighters who protect the Solar System from evil.
She is unique among all the characters in that she is stationed at the Door of Space-Time, with the specific duty of forbidding anyone to pass through it without permission. She possesses powers that are associated with time, space, the underworld, and darkness. She was one of several new characters introduced in the series' second arc (called "Black Moon" in the manga and Sailor Moon Crystal, and Sailor Moon R in the first anime adaptation), which was comparable to a retool to continue Sailor Moon past the point it was originally supposed to end.
Her role and importance differ greatly between the first anime and manga (though her personality in the two media is mostly the same). A major part of the second arc in the original manga is Pluto and Chibiusa's relationship, thus the two of them are important characters. In the anime, this relationship is not focused on and Pluto loses her prominence.