Smaug is Tolkien’s fictional dragon in The Hobbit who guards a treasure hoard.
Smaug attacks the Dwarf kingdom of Erebor and drives Thorin Oakenshield’s people into exile. He then takes the Lonely Mountain and its immense treasure, remaining there for generations before Bilbo Baggins enters the mountain during the quest to reclaim it.
Bilbo discovers that Smaug has a vulnerable area on the underside of his body. After Bilbo speaks with the dragon, the thrush in Lake-town learns of the weakness and tells Bard. Bard uses the information to shoot Smaug with the Black Arrow, killing him above Lake-town.
Tolkien created other dragons, including Glaurung and Ancalagon, but they belong to earlier First Age stories. Smaug is specifically the dragon of The Hobbit and is one of the book’s defining antagonists.