Middle-earth is the fictional region where J.R.R. Tolkien set much of The Hobbit and The Lord of the Rings.
In Tolkien’s mythology, Middle-earth is part of Arda, the world created within his larger legendarium. It is the setting for the Third Age stories of hobbits, elves, dwarves, men, and other peoples. The Shire, Rivendell, Mordor, Rohan, and Gondor are all locations in Middle-earth.
The name is related to the Old English term middangeard and to similar concepts in Germanic languages. It does not mean a planet floating between Earth and another world. Tolkien used the term as a translation connected with the human-inhabited lands of his mythology. Valinor and Númenor are also important Tolkien locations, but they are not interchangeable with Middle-earth.