What was the first Narnia book C.S. Lewis wrote?

The Lion, the Witch and the Wardrobe was the first Narnia book C.S. Lewis wrote.

Lewis began writing The Lion, the Witch and the Wardrobe in the late 1940s, and it was published in 1950. The story grew from images he had carried for years, including a faun carrying an umbrella and parcels through a snowy wood. Those images eventually developed into the tale of Lucy Pevensie and her siblings.

The Magician’s Nephew is placed first in many modern reading lists because it explains Narnia’s creation and introduces the wardrobe’s origin. However, Lewis wrote it later, and it was published in 1955 as the sixth Narnia book by publication order. That difference between writing order, publication order, and fictional chronology creates recurring confusion.

The first-written book is therefore also the first-published book: The Lion, the Witch and the Wardrobe. It was followed by Prince Caspian in 1951.