J.R.R. Tolkien’s The Hobbit features Smaug as the dragon ruling Erebor.
Smaug occupies the Lonely Mountain, also called Erebor, after driving out the dwarf king Thrór and his people. He guards the vast treasure inside the mountain, including the Arkenstone, and his occupation is the reason Thorin Oakenshield leads an expedition to reclaim the kingdom.
Bilbo Baggins first encounters Smaug while secretly entering the mountain. Their conversation is one of the book’s best-known scenes, showing Bilbo using riddling language and avoiding the dragon’s questions about his identity.
Smaug is sometimes confused with Tolkien’s other dragons. Glaurung and Ancalagon belong to the much earlier First Age stories, while Scatha appears in the history of the Rohirrim. Smaug is specifically the dragon of The Hobbit and the Third Age.