Smaug is the dragon J.R.R. Tolkien places in The Hobbit.
Smaug is a fire-breathing dragon who occupies Erebor, the Lonely Mountain, after driving out the dwarves of the Kingdom under the Mountain. His hoard includes treasure taken from the dwarves and Dale, the nearby human city. Bilbo Baggins enters the mountain as part of Thorin Oakenshield’s company and speaks with Smaug.
The dragon’s conversation with Bilbo reveals his intelligence, pride, and skill at manipulating others. Bilbo notices a vulnerable patch in Smaug’s armour-like underside, and the information eventually reaches Bard of Dale. Bard uses the Black Arrow to kill Smaug during the attack on Lake-town.
Smaug is not the dragon Glaurung, who belongs to the much earlier First Age stories associated with The Silmarillion. Nor is he Ancalagon, the great dragon defeated in the War of Wrath.