In J.R.R. Tolkien's Middle-earth, the land containing Mount Doom is Mordor.
Mordor is a dark region in the southeast of Middle-earth and the stronghold of Sauron. Mount Doom, also called Orodruin, stands there. Its volcanic fire is central to the One Ring because the Ring can be destroyed only in the fire where it was made.
In The Lord of the Rings, Frodo Baggins and Samwise Gamgee travel across Mordor after leaving Cirith Ungol. The land includes the barren plateau of Gorgoroth and the fortress of Barad-dûr, Sauron's principal stronghold.
Mordor is sometimes confused with Gondor because the two regions face one another across the mountains and are connected by the history of their wars. Gondor is a human kingdom, whereas Mordor is the territory from which Sauron wages war. The name means Black Land in Tolkien's invented language Sindarin.