Which C.S. Lewis book introduces the Pevensie children and their first journey into Narnia?

The Lion, the Witch and the Wardrobe introduces the Pevensie children and their first journey into Narnia.

Published in 1950, the novel follows Peter, Susan, Edmund, and Lucy Pevensie after they are sent away from London during the Second World War. While exploring a country house, Lucy discovers that a wardrobe opens into the snowy land of Narnia.

The children encounter Mr. Tumnus, the White Witch, and Aslan. Narnia is trapped in an endless winter under the Witch’s rule, and the arrival of the human children becomes part of the prophecy that her power will end.

The book is the first Narnia story published by Lewis, although some modern editions arrange the series in internal chronological order and place The Magician’s Nephew first. That ordering difference can cause confusion, but The Lion, the Witch and the Wardrobe remains the series’ original entry point.