Smaug is the dragon slain by Bard in J.R.R. Tolkien’s The Hobbit.
Smaug occupies the Lonely Mountain after driving the Dwarves of Erebor from their kingdom. He guards the vast treasure beneath the mountain, including the Arkenstone, and attacks Lake-town when Bilbo’s actions reveal that the Dwarves are returning.
Bard, a descendant of the former kings of Dale, learns of a vulnerable spot in Smaug’s armor from the thrush that overhears Bilbo’s conversation with the dragon. Bard uses the Black Arrow to strike Smaug in the unprotected area beneath his left breast.
Smaug is distinct from Tolkien’s other dragons. Glaurung appears in the stories of the First Age, Ancalagon is a great dragon of the War of Wrath, and Scatha is associated with the Grey Mountains. None of those dragons is the antagonist of The Hobbit.