Which Tolkien novel features the dragon Smaug as its principal dragon?

The Tolkien novel featuring the dragon Smaug as its principal dragon is The Hobbit.

Smaug occupies the Lonely Mountain and has taken the hoard of the Dwarves who once ruled there. Bilbo Baggins enters the mountain as part of Thorin Oakenshield’s company and speaks with Smaug, discovering a vulnerable area in the dragon’s armor. That information later helps Bard defeat him.

Smaug is one of Tolkien’s most memorable dragons because he combines physical menace with intelligence, pride, and persuasive speech. The Lord of the Rings contains other dragons in its historical background, but Smaug’s story belongs to The Hobbit. The Silmarillion presents earlier dragon history, including Glaurung, so readers should not confuse Smaug with Tolkien’s older First Age dragon.