The fictional world where The Chronicles of Narnia is set is called Narnia.
Narnia is the central fantasy world created by C.S. Lewis for his seven-book series, The Chronicles of Narnia. It is a land of talking animals, mythical creatures, kings and queens, and recurring conflicts between good and evil. The lion Aslan is its creator, ruler, and most important symbolic figure.
The series also includes neighboring or connected realms such as Archenland, Calormen, and the lands beyond the eastern sea. Earth, called the “world of men” in some passages, connects to Narnia through magical gateways including the wardrobe, rings, and a railway accident.
Narnia is sometimes mistakenly used as the title of the whole series, but the books are The Chronicles of Narnia. Likewise, Narnia is not the same setting as Middle-earth, which belongs to J.R.R. Tolkien. Lewis and Tolkien were friends and fellow Oxford literary scholars, but they created separate fictional worlds.