The land of Alagaësia was once protected and served by dragon riders, but since one turned against and killed the others, things haven't been the same. Through his right-hand enforcer, the evil sorcerer Durza (ROBERT CARLYLE), King Galbatorix (JOHN MALKOVICH) rules with an iron fist, and his soldiers inspire fear among the masses.
All of that's led to a guerilla rebel force, the Vardan, led by Ajihad (DJIMON HOUNSOU) and Princess Arya (SIENNA GUILLORY), the latter of whom has stolen an important stone from the King. When confronted by Durza, she uses magic to make it disappear, resulting in her imprisonment and torture to try to force her to reveal its whereabouts
Unbeknownst to any of the King's men, it's ended up in the possession of Eragon (EDWARD SPELEERS), a 17-year-old farm boy who lives with his uncle and cousin. A bit full of himself and his unproven abilities, he's entranced by tales of the days of old told by village storyteller Brom (JEREMY IRONS). Accordingly, Eragon is pleased when the stone turns out to be an egg from which hatches a baby dragon.
Having successfully hidden her from others, the dragon quickly grows up into Saphira (voice of RACHEL WEISZ) who informs Aragon -- via mental telepathy -- that he's to be her dragon rider. When Brom learns of this, he sets out to teach the boy about the ways of such a life, including that his newfound magical powers - transferred to him from Saphira -- can be both useful and dangerous.
Learning of the rebel forces and soon joined by rogue loner Murtagh (GARRETT HEDLUND), Aragon rides off on Saphira in hopes of rescuing Arya and joining the rebellion in efforts to overthrow the King and his evil, totalitarian regime.