The Hobbit is J.R.R. Tolkien’s completed children’s novel published before The Lord of the Rings.
Published in 1937, The Hobbit, or There and Back Again was written as an accessible adventure story, with a lighter tone than Tolkien’s later epic. Its central character is Bilbo Baggins, a Hobbit drawn into a journey with Thorin Oakenshield’s company to reclaim the Lonely Mountain from Smaug.
Tolkien wrote several other shorter works, including Farmer Giles of Ham and Leaf by Niggle, but those are stories or novellas rather than another completed children’s novel comparable to The Hobbit. The Silmarillion is also not the answer: it is a posthumously assembled mythology and history of Tolkien’s invented world.
The Hobbit’s commercial success was decisive. Allen & Unwin asked Tolkien for another book, and his response eventually became the much larger, darker, and more complex story published as The Lord of the Rings.