Lucy Pevensie is a fictional character in C. S. Lewis's The Chronicles of Narnia series. She is the youngest of the four Pevensie children and the first to find the Wardrobe entrance to Narnia in The Lion, the Witch and the Wardrobe. Of all the Pevensie children, Lucy is the closest to Aslan. Also, of all the humans who have visited Narnia, Lucy is perhaps the one that believes in Narnia the most. She is ultimately crowned Queen Lucy the Valiant, co-ruler of Narnia along with her two brothers, Edmund and Peter, and her sister, Susan. Lucy is the central character of the four siblings in the novels. Lucy is a principal character in three of the seven books (The Lion, the Witch and the Wardrobe, Prince Caspian, and The Voyage of the Dawn Treader), and a minor character in two others (The Horse and His Boy and The Last Battle).

The character of Lucy Pevensie was inspired by Jill Freud, a devout Catholic London girl evacuated by her convent to The Kilns, Lewis's country home in 1942, and named after Lewis's goddaughter Lucy Barfield, to whom he dedicated The Lion, The Witch and the Wardrobe. Lucy is described in the book as being fair-haired: "But as for Lucy, she was always gay and golden-haired, and all princes in those parts desired her to be their Queen, and her people called her Queen Lucy the Valiant."

Lucy was the most faithful of the four and the closest to Aslan, and never stopped believing in Narnia. She and her brothers Peter and Edmund, after dying in a train crash in England, were transported to Aslan's Country with the other Narnians.

Lucy is the most sensitive and faithful out of all her siblings; which is why she is written as seeing Aslan across the gorge in Prince Caspian and her brothers and sister written as cynical and less inclined to go on blind faith. As a young child in The Lion, the Witch and the Wardrobe in a strange house without her mother about, she is also extremely vulnerable and is looking for security, wonder and something to believe in. She is teased mercilessly by Edmund about Narnia, being accused of playing "childish games". Once she knows he also has visited the land in the wardrobe and he still maintains that they were only playing a game, her anguish knows no bounds, as her faith in humanity and the security of her own beliefs about her siblings are now also under threat.

Lucy loves animals, and befriends many creatures, and is devastated in Prince Caspian to discover that not only has Narnia been invaded by the Telmarines; but that they have suppressed the many creatures and divine and semi-divine beings that made Narnia the extraordinary place it was. Her heartfelt night-time roam through the woods, craving to see the tree spirits dance and share in their communion with nature and life once again is one of the very deep moments of love, hope and disappointment that we share with Lucy in her spiritual journey. Lucy also never stops believing in Narnia and is full of courage because of her faith; and is thus more adventurous than her sister Susan. Lucy has a great desire to help others, which is symbolised by the healing cordial that was given to her by Father Christmas for others in need and only with sparing use. The lesson from Aslan on the battlefield in The Lion, the Witch and the Wardrobe is to use this power impartially and not dwell on the needs of those she loves most.

Lucy's siblings, Peter, Susan and Edmund, do not believe her about Narnia at first, but later they all find their way to Narnia.

Lucy is the first of the Pevensies to enter Narnia through a magical wardrobe in the Professor's old house, into Narnia in the One Hundred Year Winter, under the rule of the White Witch, the evil self-proclaimed Queen of Narnia. There she meets Mr. Tumnus the Faun and, then later, the Beavers. However, her brother Edmund had also slipped into Narnia on the second occasion Lucy had entered, and encountered the White Witch while she was visiting Mr. Tumnus. Edmund, who had already jeered at Lucy about her "magical" country, continued to be spiteful towards Lucy by denying that either of them had been in Narnia. When the children all enter Narnia, Edmund slips away from the house of the Beavers and defects to the White Witch.

While travelling with Peter, Susan and Mr. and Mrs. Beaver to the Stone Table, they meet Father Christmas, who gives them gifts. Lucy is given a vial with magical cordial that can heal almost any injury, and a small dagger with which to defend herself "a great need". Edmund, meanwhile, had tried to betray the Beavers and joined the White Witch; he had first met her and been seduced by promises of power after first entering the wardrobe when trying to follow Lucy on her second entry to Narnia.