The Twenty-first Hall was a great hall on the Seventh Level in the North-end of the Dwarf realm of Khazad-dûm, in which the Fellowship camped for the night on their trek through Moria. Gandalf was able to identify the hall after the Fellowship had found the Chamber of Mazarbul.
 Portrayal in adaptations
2007: The Lord of the Rings Online:
- The Twenty-first Hall is the central base of operations for the Iron Garrison.