Peter Pevensie is the oldest of the Pevensies, and appointed head of the family by his mother when the children are sent to live in the country to escape the London bombings. When Lucy returns from her first trip to Narnia, he, along with the other children, do not believe her. He is concerned for her, and after her second trip with Edmund, he and Susan seek the advice of the wise and kind Professor Kirke.
Peter himself enters Narnia during a frantic attempt to stay out of the way of the Professor's housekeeper, and quickly assumes the role of leader. He is first to accept Mr. Beaver's help, and when Edmund later deserts them, he is prepared to risk all in order to save him. When the group meets up with Father Christmas, Peter receives a shield and a sword named Rhindon. He later uses these weapons to defend his sisters from the wolfMaugrim.
At Aslan's Camp, Peter is placed in charge of Aslan's army and leads them into battle when Aslan leaves camp unexpectedly. He fights bravely in the battle and duels the White Witch herself, and is later crowned King Peter the Magnificent, High King of Narnia. He reigned for16 years, and was the greatest king Narnia ever knew before or after. He, along with his siblings, are taken back to Our World when they stumbled upon the wardrobe during a hunting trip.
One year later, at a train station on their way to school, Peter and his siblings are summoned back to Narnia by Caspian's horn. After arriving at the ruins ofCair Paravel and meeting up with Trumpkin the dwarf, the group travels to join Caspian and his army of Narnians.
After Aslan arrives and then leaves with the girls, Peter and Edmund continue to journey with Trumpkin to the caves where the army is encamped. Once there, Peter aids in the killing of several traitors, and later gives Caspian tactical advice, which includes challenging Miraz to a duel. The Telmarine King accepts and Peter fights a one-on-one duel with him,despite the fact that Miraz is much older and stronger than he, and that the likely-hood of himself being killed is great. But Miraz is murdered by two of his generals, and Peter then fights with the Narnians and succeeds in defeating the Telmarine army.
After the battle Aslan informs Peter and Susan that they can no longer return to Narnia because they are too old. All four Pevensies then leave Narnia on Aslan's breath, and return to Our World.
What became of Peter afterwards not much is known. In 1949 ET when Peter was 22, he attended a meeting of all the Friends of Narnia. There they witnessed the apparition of Tirian pleading for help, and Peter and Edmund search for the Professor's buried Magic Rings, posing as workmen. But he is later killed in a train accident and arrives in Aslan's Country, and is counted among the faithful at the Great Reunion.