Smaug is the dragon living beneath the Lonely Mountain in J.R.R. Tolkien’s The Hobbit.
Smaug attacks and occupies Erebor, the great dwarf kingdom beneath the mountain, driving its inhabitants into exile. He takes the kingdom’s immense treasure hoard and later becomes the central obstacle in Bilbo Baggins’s adventure with Thorin Oakenshield and the company of dwarves.
Bilbo enters the mountain and speaks with Smaug, using riddling language and the name “Mr. Under-treasure.” During their conversation, Bilbo notices a vulnerable patch in the dragon’s armor-like hide. The information eventually reaches Bard of Dale, who kills Smaug with the Black Arrow after the dragon attacks Lake-town.
Smaug is often confused with other dragons in Tolkien’s legendarium. Glaurung belongs to the First Age stories, Ancalagon is a dragon of the War of Wrath, and Scatha is associated with the Grey Mountains. Only Smaug is the dragon of The Hobbit’s Lonely Mountain.