The French Emperor Charlemayn has occupied Spain for seven years. So far, however, he has not conquered the city of Saragossa, an outpost of Islam (which the poet categorizes as a form of paganism) that’s ruled by King Marsilion. Marsilion, for his part, fears that he can’t conquer Charlemayn. Marsilion’s advisor, Blancandrin, suggests that he send an envoy promising eventual submission to Charlemayn and conversion to Christianity. Marsilion agrees. Marsilion’s messengers find Charlemayn celebrating a recent victory at Cordova. The deliberative Charlemayn broods over Marsilion’s offer, not sure if the pagan king can be trusted. His trusted barons concur that the pagans are probably plotting something. The only exception is Count Roland, Charlemayn’s nephew, who argues for war. Roland’s stepfather, Count Ganelon, urges Charlemayn not to trust Roland. Charlemayn agrees to accept the envoys’ offer and sends Ganelon as messenger at Roland’s suggestion. Roland’s nomination of Ganelon infuriates Ganelon, and on his way to Saragossa, he plots with Blancandrin to kill his stepson. When Ganelon meets King Marsilion, he persuades the king to launch an ambush of the rear-guard of Charlemayn’s retreating army, which Ganelon knows will contain Roland.
When Ganelon returns to Charlemayn’s camp, he persuades the emperor to return home to France, and that Marsilion will soon journey to Aix to pledge himself as Charlemayn’s vassal. Satisfied, Charlemayn departs with his army, but he has troubling dreams of treachery. Despite his foreboding, he appoints Roland to the rear-guard which will stay at Roncevaux Pass to protect the army’s homeward retreat.
When the rear-guard hears the Saracens approaching, Roland’s best friend, Oliver, urges him to blow his Olifant (a massive horn) to summon help from Charlemayn, but Roland pridefully refuses. Archbishop Turpin exhorts the men to fight for Christendom, and at first, it looks as if they will easily prevail over their enemies. However, as more and more French peers are felled by Paynims (pagans), the tide turns against them. When Roland decides to blow the Olifant after all, Oliver blames him for waiting too long. Turpin urges him to do it anyway. When Roland finally sounds the horn, Ganelon tries to dissuade Charlemayn from riding to the rescue, revealing himself as a traitor.
After Oliver is fatally stabbed, he and Roland reconcile as Oliver dies. Soon, Roland, Turpin, and Walter Hum are the only remaining Franks. After Walter dies and Charlemayn’s approach is evident, the Paynims flee, leaving Roland free to gather the bodies of the many slain. Turpin dies after blessing the dead. Roland realizes that he, too, is dying, so he walks toward Spain with his Olifant and his faithful sword, Durendal. Unable to destroy Durendal’s blade, Roland dies with the sword tucked underneath him in the hope that no pagan will steal it and tarnish its honor.
When Charlemayn finds that his men have been slaughtered, he grieves sorely and prays for the sun to stand still so that he can pursue the Saracens back to Saragossa. God grants this, and he succeeds in driving them back. While Charlemayn is sleeping that night, however, Baligant, emir of Babylon, arrives in Saragossa with a massive navy. He makes an agreement with Marsilion—who is dying from a wound that Roland inflicted upon him—to conquer Charlemayn in exchange for the land of Spain.
The next morning, Charlemayn returns to Roncevaux Pass and grieves passionately over Roland’s remains. Before he can depart for France with Roland’s body, however, he is stopped by Baligant’s envoys. Despite Charlemayn’s sorrow, he promptly accepts Baligant’s challenge and accordingly musters his army.
Baligant, with a huge host of Paynims from various lands, faces Charlemayn’s army. Though the combat is close and bloody, the Paynims are gradually outmatched. After Charlemayn kills Baligant’s son Malpramis, Baligant is determined to kill Charlemayn personally. Baligant refuses to convert to Christianity and yield to Charlemayn, so, after he lightly wounds the emperor, Charlemayn kills him. The remaining Paynims flee.
Charlemayn’s army occupies Saragossa, where they destroy all non-Christian houses of worship and force 100,000 people to be baptized. The next day, Charlemayn journeys back to France, taking Marsilion’s widow, Queen Bramimond, with him. He then summons all his vassals to Aix for Ganelon’s trial. Ganelon continues to insist upon his innocence—he claims he took vengeance against Roland, but was not treasonous. The trial is inconclusive until a baron named Thierry demands Ganelon’s death and faces Ganelon’s friend and champion Pinabel in single combat. After Pinabel is killed, Ganelon is brutally executed, along with 30 of his kinsmen who supported him.
Queen Bramimond becomes convinced of the truth of Christianity and is baptized, taking the new name Juliana. That night, before Charlemayn can finally rest, he is summoned by the angel Gabriel to fight Paynims in another city, and he laments his wearisome life of continual combat.
