In ages past; the world of Spira experienced a golden age of perfection brought about by an advanced civilization through the use of wondrous machinery called machina..
However around one thousand years before the present day a colossal menace known only as Sin appeared and sundered all before it. Though a line of summoners have since brought Sin low many times it inevitably returns in an unending cycle of destruction. In the face of this ever-pervasive threat the people of Spira flocked to the teachings of Yevon which tell that Sin is a punishment to those who relied overly on machina.
Tidus is a young Blitzball star that mysteriously finds himself in Spira after his home city of Zanarkand is destroyed by Sin one thousand years in the past. Believing Sin to be the key to returning home Tidus joins a young summoner named Yuna on her pilgrimage to destroy Sin and bring about the Calm.