In what fictional world is The Hobbit set?

The Hobbit is set in the fictional world of Middle-earth.

More precisely, its story takes place mainly in the northwestern parts of Middle-earth, including the Shire, Rivendell, the Misty Mountains, Mirkwood, Lake-town, and the Lonely Mountain. Bilbo Baggins begins in the Shire and travels eastward with Thorin Oakenshield’s company.

Middle-earth is not simply another planet in Tolkien’s mythology. It is the central inhabited continent of Arda, Tolkien’s imagined version of Earth in a remote prehistoric age. The events of The Hobbit occur during the Third Age, in the year 2941 by Tolkien’s chronology.

Readers sometimes confuse Middle-earth with a complete name for the entire universe or with a modern fantasy realm like Narnia. Tolkien used Middle-earth both for the continent itself and, more loosely, for the broader setting of his legendarium. The Hobbit and The Lord of the Rings are both set there.