In J.R.R. Tolkien’s legendarium, Smaug is the dragon who lives beneath the Lonely Mountain.
Smaug occupies Erebor after driving the dwarves of Durin’s Folk from their kingdom. In The Hobbit, Thorin Oakenshield’s company travels there to reclaim the mountain and its treasure, with Bilbo Baggins acting as the burglar.
Bilbo discovers that Smaug has a vulnerable patch in his armour-like underside. He later reports this information to Bard, who uses the knowledge to kill the dragon with the Black Arrow.
Smaug is distinct from Tolkien’s other dragons. Glaurung belongs to the First Age stories, while Ancalagon the Black is associated with the War of Wrath. Smaug’s role is specifically tied to Erebor, Dale, Bilbo, and the events of The Hobbit.