J.R.R. Tolkien gives the underground dwarf kingdom later called Moria the name Khazad-dûm.
Khazad-dûm was the greatest realm of the Dwarves in Middle-earth. It was built beneath the Misty Mountains and became wealthy through mining, especially after the discovery of mithril. The Dwarves’ prosperity attracted danger, and their mining eventually awakened a Balrog beneath the mountains.
After the Dwarves abandoned the kingdom, it became known as Moria, a name associated with darkness and dread. The Fellowship of the Ring travels through its ruined halls after the gates of Caradhras prove impassable. In the underground chamber, Gandalf confronts the Balrog on the Bridge of Khazad-dûm.
Khazad-dûm is the Dwarvish name, while Moria is the name most familiar to readers of The Lord of the Rings. Erebor is a different dwarf kingdom, the Lonely Mountain featured in The Hobbit. Nogrod and Belegost are older Dwarven cities connected with the First Age.