Final Fantasy: The Spirits Within is a 2001 adult animated science fiction film directed by Hironobu Sakaguchi, creator of the Final Fantasy franchise. It was the first photorealistic computer-animated feature film and the most expensive video game-inspired film until the release of Prince of Persia: The Sands of Time in 2010. The film stars the voices of Ming-Na Wen, Alec Baldwin, Donald Sutherland, James Woods, Ving Rhames, Peri Gilpin, and Steve Buscemi, and follows scientists Aki Ross and Doctor Sid in their efforts to free a post-apocalyptic Earth from the Phantoms, a mysterious, deadly alien race who has driven the remnants of humanity into "barrier cities". Aki and Sid must fight against General Hein, who wants to use more violent means to end the conflict.

Square Pictures rendered the film using some of the most advanced processing capabilities available at the time. A render farm of 960 workstations was tasked with rendering each of the film's 141,964 frames. It took a staff of 200 about four years to complete The Spirits Within. Square intended to make the character of Aki Ross into the world's first photorealistic computer-animated actress, with plans for appearances in multiple films in different roles.

The Spirits Within premiered in Los Angeles on July 2, 2001, and was theatrically released in the United States on July 11. It received mixed reviews, but was widely praised for its characters' realism. Due to rising costs, the film greatly exceeded its original budget toward the end of production, reaching a final cost of $137 million (equivalent to $214 million in 2023); it grossed only $85.1 million at the box office. The film has been called a box-office bomb and is blamed for the demise of Square Pictures.