Kingdom Hearts is a series of action role-playing video games developed and published by Square Enix. It is the result of a collaboration between Square and Disney Interactive Studios. Kingdom Hearts is a crossover of various Disney settings based in a universe made specifically for the series. The series features a mixture of familiar Disney and Final Fantasy characters, as well as several new characters designed by Tetsuya Nomura.

We can find 19 Final Fantasy characters in the Kingdom Hearts saga.

In Kingdom Hearts, Tidus and Wakka from Final Fantasy X and Selphie from Final Fantasy VIII can be seen in the Destiny Islands. The three appear in the first game and are available for fighting practice. Tidus and Wakka do not appear in Kingdom Hearts II, though they are mentioned by Selphie, who briefly makes an appearance with Kairi. Squall Leonhart from Final Fantasy VIII, as well as Aerith Gainsborough, Yuffie Kisaragi and Cid Highwind from Final Fantasy VII meet with Sora, Donald and Goofy in Traverse Town. Cloud Strife from Final Fantasy VII appears as a possible antagonist in Olympus Coliseum, too.

In Kingdom Hearts II, Squall Leonhart, Aerith Gainsborough, Yuffie Kisaragi, and Cid Highwind reappear in Hollow Bastion/Radiant Garden as the "Hollow Bastion Restoration Committee" to rebuild the place after they came back from Traverse Town, with the addition of Tifa Lockhart, Sephiroth and Cloud Strife from Final Fantasy VII. Cloud is now looking for Sephiroth to defeat him. Sephiroth can be fought later in the game after clearing certain stages, while Yuna, Rikku and Paine from Final Fantasy X-2 are seen as fairies. Auron from Final Fantasy X makes an appearance in Olympus Coliseum hired by Hades to defeat Hercules, but he ends up rebelling against Hades and aiding Sora and his friends. In Twilight Town, Setzer Gabbiani from Final Fantasy VI is seen as the Struggle Champion, while Seifer Almasy, Raijin (Rai) and Fujin (Fuu) from Final Fantasy VIII appear as the "Twilight Town Disciplinary Committee" with Vivi Orunitia from Final Fantasy IX as their friend.