The Dwarven kingdom beneath the Lonely Mountain in J.R.R. Tolkien’s works is Erebor.
Erebor is the Sindarin name for the Lonely Mountain, and it is also used for the Dwarven realm established there. The kingdom becomes wealthy through its mining and craftsmanship, attracting the attention of the dragon Smaug. Smaug attacks, drives out the Dwarves, and takes possession of the mountain’s treasure.
In The Hobbit, Thorin Oakenshield leads an expedition to reclaim Erebor. Bilbo’s discovery of the Arkenstone and the death of Smaug are among the events that transform the mountain’s political future. Dáin Ironfoot later becomes king after Thorin dies in the Battle of Five Armies.
Erebor is often confused with Moria, whose Dwarven name is Khazad-dûm. Moria lies beneath the Misty Mountains and has a different history. Belegost is another ancient Dwarven city, located in the Blue Mountains. These locations are distinct from the Lonely Mountain and its kingdom.