In the fiction of J. R. R. Tolkien, Belegost was one of two Dwarven cities in the Ered Luin. Belegost translates from Sindarin as "Great Fortress". Tolkien used Mickleburg as an Anglicization of the Westron form of the name. The dwarves themselves called it by its Khuzdul name, Gabilgathol of unknown meaning.
Belegost lay to the north of its neighbouring dwarven city Nogrod, and was the home of the Dwarven people known as Broadbeams. Its only named king, Azaghâl, was killed by Glaurung in the Nirnaeth Arnoediad.
The Dwarves of Belegost were friends to the Sindar and later also the Noldor of Beleriand. They did not join the Dwarves of Nogrod in the Sack of Doriath, and actually attempted to dissuade their friends from it.
Unlike Nogrod to the south, Belegost may have partly survived after the War of Wrath, although it was recorded as having been 'ruined' at that time: many Dwarves of Belegost joined Durin's folk in Khazad-dûm 60 years after the war, but the Ered Luin still remained home to Dwarves until at least the early Fourth Age, including some of Durin's folk.
Bifur, Bofur and Bombur, who lived in the Blue Mountains until the events described in The Hobbit in the late Third Age, were not kinsfolk of Thorin Oakenshield, as were the rest of his dwarven companions during the Quest of Erebor: it seems likely that they were Broadbeam dwarves.
