For 1000 years, the world of Spira was held in the grip of terror as the great monster Sin punished it's citizens for using the forbidden machina in the great wars. To combat Sing, powerful summoners would make a pilgrimage to Zanarkand, the ruins of what was once the greatest city in Spira. Able to call and control the devastating manifestations of the fayth, aeons, into battle, these summoners would sacrifice their lives and the life of a chosen guardian, to defeat Sin for a temporary period of time called the "Calm." Unfortunately, the Calm would end and Sin would eventually returne, forcing a new summoner to forfeit their life to bring peace to Spira once again.

This cycle of life and death continued in Spira for untold generations, until one summoner stood against the teachings of Yevon and sought a new means by which to defeat Sin -- permanentely. The sommoner's name was Yuna, and along with her guardians, went against the order of Yevon and fought enemies on all sides. In a last ditch effort, Yuna and her guardians took on Sin and defeated it forever, bringing forth a time that would be referred to as the "Eternal Calm." Although peace would finally last forever, Yuna was forced to say goodbye to someone whom she cared for very much. The young man named Tidus had been a dream of the Fayth, and when the Fayth were defeated during the attack on Sin, their dream faded.

Yuna thought that the lover of her life had vanished alongside the last remaining traces of Sin. But two years later, Rikku appeared in Besaid Village and delivered a sphere found by Kimahri, Yuna's former guardian and the new Elder of the Ronso tribe of Mt. Gagazet. This sphere contained images of a man who resembled Tidus so closely that Yuna was compelled to leave Besaid and begin a new search for more spheres that might lead her closer to the truth. This game is her story.