Tidus (Japanese: ティーダ, Hepburn: Tīda) is a character in Square Enix's video game series Final Fantasy and the main protagonist of the 2001 role-playing video game Final Fantasy X. A 17-year-old athlete from the city of Zanarkand, he is transported to Spira after Sin destroys Zanarkand. Shortly after arriving there, Tidus meets the summoner Yuna and her guardians and joins them on a pilgrimage to kill Sin after learning that it is his missing father, Jecht. Tidus has appeared in other video games, including the Final Fantasy X sequel X-2, where he can be recruited as a playable character in the international version. He also appears in various Square Enix crossover games and in the Kingdom Hearts series, where he is depicted as a child.

Tetsuya Nomura designed Tidus with a cheerful personality and appearance to contrast with previous Final Fantasy protagonists. Scenario writer Kazushige Nojima wanted to expand the relationship between player and character with monologues describing the game's setting. The narrative was initially focused on the romance between Tidus and Yuna, but Square Enix instead decided to focus on Tidus' relationship with Jecht to have a greater impact on the setting. Tidus is voiced in Japanese by Masakazu Morita, who also performed his motion capture, and in English by James Arnold Taylor; both actors enjoyed voicing the character.

Tidus has been generally well-received by video-game critics. His cheerful personality and heroism make him an appealing protagonist, contrasting with previous male characters in the franchise and being comparable to messiah figures and other fictional heroes. Tidus' character development and romantic relationship with Yuna are considered among the best in video games, although reviewers and fans were divided on Taylor's voice acting. Tidus has been popular with fans, often ranking in polls as one of the best Final Fantasy characters. Action figures and jewelry related to Tidus have been produced, and he is a popular character among cosplayers.

Before the development of Final Fantasy X, game-scenario writer Kazushige Nojima was concerned about the relationship between the player and the main character in a Final Fantasy title, and wanted to make the story easier to follow. Because the player and the main character find themselves in a new world, Nojima wanted Tidus' understanding of that world to track the player's progress in the game. Nojima felt that Tidus was the easiest character to draw in the first half of Final Fantasy X, because the player and characters learn about the story together. Nojima created a brief description of Tidus for character designer Tetsuya Nomura, from which Nomura created a sketch for input from Nojima and other staff members. Nomura was asked to design Tidus differently from the game's theme so he would stand out. Movie director Hiroshi Kuwabara noted the difficulty of making Tidus and the other main characters realistic. The staff wanted to introduce an undead playable character, but after Nojima saw a film with a similar idea for its protagonist during the game's development, the role of an undead person was then given to secondary character Auron. Director Yoshinori Kitase stated that during the development of Final Fantasy X, one developer focused on the romance between Tidus and Yuna.

Nomura stated that the contrast between Tidus and Yuna was established by their names, which are derived from the Okinawan words for "sun" and "night", respectively. This contrast is also shown in the items that power their celestial weapons; the sun sigil and crest for Tidus, and the moon sigil and crest for Yuna. Because the player can change Tidus' name, his name is not spoken in the game. However, a character in Dream Zanarkand uses Tidus' name in a dialogue box, and it appears in Spiran script on the nameplate of an Auroch locker in the Luca stadium. Before Final Fantasy X's release, Tidus was known to the media as Tida. In early 2001, PlayOnline changed the character's name to "Tidus". Because Tidus' name is never spoken in FFX, its intended pronunciation has been debated. Interviews with James Arnold Taylor and spoken dialogue in the English versions of Dissidia Final Fantasy, Dissidia 012 Final Fantasy, and Kingdom Hearts, in which Tidus makes cameo appearances, indicate his name is pronounced /ˈtiːdəs/ (TEE-dəs); in the English version of Kingdom Hearts II, Tidus' name is pronounced /ˈtaɪdəs/ (TY-dəs). According to Taylor, the name was pronounced TEE-dəs during the localization of FFX because the narrator of an early English trailer pronounced it that way.

Nojima said that he cried during the game's ending, when Tidus and Yuna are separated and he vanishes. For the sequel, Final Fantasy X-2, producer Kitase thought that the greatest fan expectation was the reunion of Tidus and Yuna after their separation in the first game. The game generated rumors about Tidus' connection with the villain Shuyin, who was physically similar to him and had the same voice actors. However, according to Square Enix, given Tidus' nature, such a storyline would be too complicated. For the remastering of Final Fantasy X and X-2, producer Kitase's motivation was to have people too young to have played the games experience them; his son was only old enough to know Tidus and Yuna from Dissidia Final Fantasy and its prequel.

Character designer Nomura said that he wanted Tidus' clothing and accessories to suggest a relationship with the sea. Tidus' clothing has a distinctive blue motif; his blitzball team logo, which is based on a fish hook, is an amalgam of the letters J and T, the first letters of his name and that of his father Jecht. Additionally, he and Yuna share the key color blue, suggesting a maritime link.

Tidus was designed to be distinctive within Spira. Because of improvements in technology following the previous Final Fantasy games, Nomura wanted to make Tidus' face more realistic and his build more noticeable compared to previous Final Fantasy characters, who looked scrawny. Square Enix wanted Tidus to have an Asian look. Artist Yusuke Naora worked on Tidus' design and his relationship with the sea, which he found difficult to draw and translate into computer-generated imagery CGI.