The central landmass in many of J.R.R. Tolkien’s stories is called Middle-earth.
Middle-earth is the setting for The Hobbit and The Lord of the Rings, as well as many stories later collected in The Silmarillion and related works. It is not the entire universe of Tolkien’s mythology. Rather, it is a region of Arda, the world created within Tolkien’s fictional cosmology.
The name is related to the Old English term middangeard and to similar expressions in Germanic languages. Tolkien used it for a mythic version of the ancient world, not as a simple synonym for a planet or a continent in every context.
Other important places lie outside Middle-earth. Valinor is a realm in Aman, west of Middle-earth, while Númenor is an island kingdom with its own separate history. Readers sometimes use Middle-earth to mean all of Tolkien’s mythology, but Tolkien’s geography and terminology distinguish it from these surrounding regions.