Which author and C.S. Lewis friend created Middle-earth?

J.R.R. Tolkien created Middle-earth and was a close friend of C.S. Lewis.

Tolkien was an English writer, philologist, and university professor best known for The Hobbit and The Lord of the Rings. Middle-earth is the main setting of much of his legendarium, including the histories of Elves, Men, Dwarves, and other peoples.

Lewis and Tolkien met at Oxford and became members of the informal literary group known as the Inklings. They read drafts of their work aloud to one another and discussed mythology, language, Christianity, and literature. Tolkien’s encouragement helped Lewis during a period when Lewis was moving back toward Christian belief.

The two authors were not co-creators of Narnia or Middle-earth. Lewis wrote the Chronicles of Narnia, while Tolkien wrote the Middle-earth stories. Their friendship is sometimes oversimplified because both used mythic fantasy, but their invented worlds, characters, and literary histories are distinct.