Cait Sith (ケット・シー, Ketto Shī; /keɪt sɪð/ in English, /kæt ʃiː/ in Japanese) is a character in the 1997 role-playing video game Final Fantasy VII developed by Square. He reappeared in Final Fantasy VII Remake and Final Fantasy VII Rebirth, developed and published by Square Enix. Taking its name from the Scottish mythology fairy Cat-sìth, he is a fortune-telling robot that initially joins the group to act as a spy for the Shinra Electric Power Company, controlled remotely by their employee Reeve Tuesti (リーブ・トゥエスティ, Rību Tuesuti). After his betrayal is revealed, he joins the protagonists fully to help stop an impending disaster to the planet. In English Cait Sith is voiced by Greg Ellis and Paul Tinto, while in Japanese he is voiced by Hideo Ishikawa. Reeve meanwhile is voiced by Jamieson Price and Jon Root in English, and Banjô Ginga in Japanese.

Named after the Scottish mythology fairy Cat-sìth, Cait Sith was designed by lead Tetsuya Nomura to be two characters combined into one, a concept he wanted to include since the beginning of development. Designed as a small anthropomorphic cat resembling the fictional character Puss in Boots but with a crown, Cait Sith uses a megaphone to control the other half of his body, with the effectiveness of his control determined by the quality of his megaphone. During development Nomura was conflicted with using either a fat moogle or fat chocobo, two recurring creature types in the Final Fantasy series, for Cait Sith's other half. He chose the former, with Cait Sith riding atop its shoulders while it walked by hopping and skipping along. Nomura stated in an interview with Young Jump that characters like Cait came about from a desire to develop unique characters for the game due to it being his first full project and his own nervousness, and at the time such character concepts would normally be considered "unreasonable".

Cait Sith was intended to speak with a Kansai Japanese dialect, and they brought a specialist to assist with writing his dialogue properly. This was done to give his dialogue a "humorous" feel, even in the most serious scenes. However, when the game was released players remarked that his dialogue did not fit the dialect, so the development team instead called it "a Cait Sith dialect". Meanwhile, as of Advent Children, a film sequel to the original game, he speaks with a Scottish accent in English localizations.

Originally, it was planned to have the character to be able to capture monsters, and fight using a whip and throwing cards. In the final game he has a Limit Break attack usable after taking or dealing enough damage during the course of battles, where a slot machine will appear on the screen. Depending on the outcome, one of several various effects will occur, including either instantly defeating all present enemies, or with the player's party instantly defeated instead. For Final Fantasy VII Rebirth, part of a series of titles serving as a remaking of the original game, battle director Teruki Endo had a difficult time developing his gameplay aspect. Believing there were two approaches to gameplay archetypes, "standard" and "oddball", he went with the latter due to Cait Sith's appearance while tweaking it up until the final stages of develop to ensure "it didn't have too many quirks".

In a change from previous entries in the Final Fantasy series, the development team worked off of Nomura's character designs directly. Standing 100 cm (3 ft 4 in) tall, Cait Sith resembles a bipedal tuxedo cat with gray fur, having a white belly, tail tip, paws, and a patch in an upward-pointing triangle pattern on his face. His outfit consists of a pair of boots, white gloves, a red cape, and a crown atop his head, while his eyes are always in a closed state. The other half of its body is a large fat moogle, and while its height is not stated it stands significantly taller and wider than Cait Sith. It appears as a rotound, white bipedal furry creature, which two bat wings protruding from its back and a wide mouth with two tusks protruding from its lower jaw. Reeve meanwhile stands 180 cm (5 ft 11 in) tall, and has long black hair slicked back and a trimmed beard, wearing a blue suit with a red tie.

The character model was reimagined by Masaaki Kazeno for Final Fantasy VII Remake. Kazeno aimed for cuteness in his design and unveiled it at a meeting during Remake's development, only to be surprised when he was informed Cait Sith was not going to be a playable character until the next title, Final Fantasy VII Rebirth. His height was shortened as of Rebirth, now standing 80 cm (2 ft 8 in) tall. Reeve meanwhile was redesigned by artist Roberto Ferrari for the games, given a black pinstripe suit, which Ferrari felt made him look "suave".

Cait Sith is a robotic talking cat. In Final Fantasy VII, he rides atop an unnamed robotic Moogle; in later installments in the Compilation of Final Fantasy VII, he either walks by himself or rides Red XIII. As a robot, he can be rebuilt and replaced and is controlled by Reeve Tuesti, whose original intent during Final Fantasy VII was to infiltrate Cloud's group and sabotage their resistance efforts on behalf of his Shinra employers. After having a change of heart, he decides to help the group, even risking his life by destroying a version of himself to extract the Black Materia Sephiroth needs to summon the Meteor spell. He appears briefly in Advent Children and Final Fantasy VII Remake and as a briefly playable character throughout Dirge of Cerberus.

Cait Sith is voiced in English by Greg Ellis in Advent Children and Dirge of Cerberus and by Paul Tinto in Final Fantasy VII Rebirth, while Hideo Ishikawa voices him in Japanese. Reeve is voiced in English by Jamieson Price in Advent Children and Dirge of Cerberus and by Jon Root in Final Fantasy VII Remake, Banjō Ginga provides his voice in Japanese.