Middle-earth is the central region of the fictional world in J.R.R. Tolkien’s The Hobbit and The Lord of the Rings. The name refers to the inhabited lands where many of Tolkien’s best-known stories occur, including the Shire, Rohan, Gondor, Mirkwood, and Mordor.
The term is a modern English rendering of an older Germanic and Norse idea of the human world between different cosmic realms. Tolkien did not intend Middle-earth to mean an entire planet or a separate universe. In his mythology, it is part of Arda, the world where the broader history of his legendarium unfolds.
Valinor, Númenor, and Beleriand are related but distinct places or regions. Valinor lies in the Blessed Realm, Númenor was an island kingdom later destroyed, and Beleriand was a major First Age land that was reshaped or lost before the main events of The Lord of the Rings.