Final Fantasy IV (ファイナルファンタジーIV Fainaru Fantajī Fō?) is a role-playing video game developed and published by Square (now Square Enix) in 1991 as a part of the Final Fantasy series. The game was originally released for the Super Famicom in Japan and has since been rereleased for many other platforms with varying modifications. The game was re-titled Final Fantasy II during its initial release outside of Japan as the original Final Fantasy II and Final Fantasy III had not been released outside of Japan at the time. However, later localizations used the original title.

The game's story follows Cecil, a dark knight, as he tries to prevent the sorcerer Golbez from seizing powerful crystals and destroying the world. He is joined on this quest by a frequently changing group of allies. Final Fantasy IV introduced innovations that became staples of the Final Fantasy series and role-playing games in general. Its "Active Time Battle" system was used in five subsequent Final Fantasy games, and unlike prior games in the series, IV gave each character their own unchangeable character class.

With its character-driven plot, use of new technologies and critically acclaimed score by Nobuo Uematsu, Final Fantasy IV is regarded as a landmark of the series and the role-playing genre. The various incarnations of the game have sold more than four million copies worldwide. An enhanced remake, also called Final Fantasy IV, with 3D graphics was released for the Nintendo DS in 2007 and 2008. A sequel, Final Fantasy IV: The After Years, was released for Japanese mobile phones in 2008, and worldwide via the Wii Shop Channel on June 1, 2009. In 2011, both Final Fantasy IV and The After Years were released for the PlayStation Portable as part of the compilation Final Fantasy IV: The Complete Collection, which also included a new game, set between the two; Final Fantasy IV: Interlude. An iOS port of the Nintendo DS remake was released on December 20, 2012, as well as an Android version on June 4, 2013.