Which of Tolkien’s children’s books features the dragon Smaug?

The dragon Smaug appears in J.R.R. Tolkien’s The Hobbit.

Smaug is the dragon who occupies the Lonely Mountain after driving out the Dwarves of Erebor. The novel’s central adventure follows Bilbo Baggins, Thorin Oakenshield, and a company of dwarves as they travel toward the mountain to reclaim its treasure. Bilbo discovers a weakness in Smaug’s armour and later reveals it to Bard of Lake-town.

Smaug is sometimes confused with other dragons in Tolkien’s legendarium, such as Glaurung and Ancalagon the Black. Those figures belong to the much earlier histories associated with The Silmarillion. Smaug belongs specifically to the Third Age and to the story of The Hobbit. His name also helps distinguish the novel from Peter Jackson’s later film adaptation, which expands some events and includes material drawn from Tolkien’s appendices.