J.R.R. Tolkien calls the dragon’s mountain home Erebor in The Hobbit.
Erebor is the Sindarin name for the Lonely Mountain, a major kingdom and stronghold of the Dwarves. Under King Thrór and his descendants, it became famous for its wealth and craftsmanship. The dragon Smaug attacked the mountain, drove out the Dwarves, and took their treasure as his hoard.
Bilbo Baggins travels to Erebor with Thorin Oakenshield and the other Dwarves. He enters the mountain and speaks with Smaug, helping expose the dragon’s vulnerable spot. After Smaug leaves to attack Lake-town, Bard kills him, and the Battle of the Five Armies follows near the mountain.
Erebor should not be confused with Mount Doom, the volcanic peak in Mordor, or Moria, the ancient underground Dwarven city. “The Lonely Mountain” is the common English name, while “Erebor” is its distinctive Tolkienian name.