Aslan (/ˈæslæn, ˈæz-/) is a major character in C. S. Lewis's The Chronicles of Narnia series. Unlike any other character in the Narnian series, Aslan appears in all seven chronicles. Aslan is depicted as a talking lion and is described as the King of Beasts, the son of the Emperor-Over-the-Sea, and the King above all High Kings in Narnia.

C. S. Lewis often capitalises the word lion in reference to Aslan since he parallels Jesus as the "Lion of Judah" in Christian theology. The word aslan means "lion" in Turkish.

Aslan is first mentioned by Mr. Beaver when the Pevensie children arrive in Narnia. He is described by Mr. Beaver as being the true king of Narnia who has returned to help the Pevensies to free Narnia of the White Witch's rule.

Mr and Mrs. Beaver guide Peter, Susan and Lucy to the stone table to meet Aslan. They inform Aslan that Edmund has betrayed them by joining the White Witch. Aslan sends some of his followers to rescue Edmund. The next day, Aslan is approached by the White Witch who demands her right to kill Edmund, as the deep magic states that all traitors belong to her. Aslan discusses the matter in private with the Witch, persuading her to release Edmund.

That same night, Aslan travels to the stone table with Susan and Lucy. The Witch and her followers bind Aslan to the stone table – it is revealed that Aslan had agreed to be killed to save Edmund. However, due to a deeper magic (which the Witch was unaware of), Aslan is brought back to life and manages to rescue his followers who have been turned to stone by the Witch. He brings his followers to the battle where he kills the Witch himself, ending her tyranny once and for all.

Aslan is present at the coronation of the four Pevensie children. He then leaves to attend to other duties with Mr. Beaver convincing the Pevensie children that he will be coming and going.

The Pevensies are summoned into Narnia from their world to help Caspian – the rightful King of Narnia – overthrow his usurping Uncle Miraz and restore freedom to the land. When they get lost in the forest, Aslan calls Lucy to lead her siblings to him; some obey more faithfully than others. Aslan helps Peter, Edmund, and Trumpkin the Dwarf to come to Caspian's aid in time to thwart an attempt on his life. Aslan then leads an army of awakened Trees and Maenads to victory against Miraz's Telmarine occupation. He later crowns Caspian as King and creates a door whereby surviving Telmarines can leave the Narnian world if they so choose.

Edmund and Lucy Pevensie are transported to the eastern ocean of the Narnian world along with their cousin, the recalcitrant Eustace, where they join King Caspian on a seafaring journey. When Eustace falls under an enchantment and becomes a dragon, Aslan delivers him from the enchantment. Aslan appears at various points of the journey to provide guidance. When they reach the world's end, Aslan appears as a lamb before returning to his usual form. He shows Reepicheep (a talking mouse) the way to Aslan's Country.