J.R.R. Tolkien features Smaug as the main antagonist in The Hobbit.
Smaug is a powerful fire-breathing dragon who occupies the Lonely Mountain and guards the treasure of the Dwarves of Erebor. He drove the Dwarves from their kingdom before the events of the novel, creating the central reason for Thorin Oakenshield’s quest.
Bilbo Baggins enters the mountain as the company’s burglar and speaks with Smaug. Their conversation reveals Bilbo’s cleverness but also allows Smaug to infer that Lake-town may be involved in the Dwarves’ return. Smaug later attacks Lake-town, where Bard kills him with the Black Arrow.
Tolkien created several other dragons in his wider mythology, including Glaurung and Ancalagon the Black. Those figures belong primarily to the stories of the First Age, so they are not alternative names for the dragon in The Hobbit. Smaug remains Tolkien’s best-known dragon character.