J.R.R. Tolkien’s The Lord of the Rings mainly takes place in Middle-earth.
Middle-earth is the central continent of Tolkien’s imagined world during the later parts of its history. The Lord of the Rings travels through regions including the Shire, Rivendell, Rohan, Gondor, Mordor, and the Misty Mountains.
The term comes from older Germanic and English expressions related to the inhabited world. Tolkien used it as a translation or modernization of a concept rather than as the name of an entire planet.
Valinor is a blessed land in Aman, Númenor is an island kingdom of Men, and Beleriand is a western region important to the First Age. These places belong to Tolkien’s wider mythology but are not the main setting of The Lord of the Rings.