The fictional land in C.S. Lewis’s Narnia novels is Narnia.
Narnia is the central setting of The Chronicles of Narnia, a series of seven books published between 1950 and 1956. Lewis populates the land with talking animals, mythical creatures, kings, queens, and supernatural forces. The series begins with The Lion, the Witch and the Wardrobe in its publication order.
Narnia is not simply another name for Earth. Several stories connect Narnia with other worlds through magical portals, including a wardrobe, a railway platform, and a pool. The children who visit it come from Earth, but Narnia has its own history, geography, rulers, and calendar.
Readers sometimes mix Narnia up with Middle-earth, J.R.R. Tolkien’s setting, or Neverland, J.M. Barrie’s setting. Those are separate fictional worlds created by different authors. Narnia is specifically Lewis’s world, and its best-known ruler is the lion Aslan.