Most of J.R.R. Tolkien’s best-known stories occur in the fictional region called Middle-earth.
Middle-earth is the setting for The Hobbit and The Lord of the Rings, as well as much of The Silmarillion. It is a large landmass in Tolkien’s imagined world of Arda, and the events described in the books take place during different historical ages.
The name does not mean a planet named Middle-earth. Tolkien adapted the concept from older Germanic and English expressions for the inhabited world, including the Old English term middangeard. In the fiction, Middle-earth is only one part of a wider cosmological setting.
Númenor, Valinor, and Beleriand are also important locations in Tolkien’s legendarium, but they are not interchangeable with Middle-earth. Númenor is an island kingdom, Valinor is a realm in Aman, and Beleriand is a region of the First Age.