Morannon is the Sindarin name for the Black Gate of Mordor in J.R.R. Tolkien’s works. The gate forms the main entrance to Mordor and is built into the mountainous barrier that protects Sauron’s realm.
In The Lord of the Rings, the Gate is guarded by Sauron’s forces and becomes the destination of the army led by Aragorn and the leaders of the West. Their march to the Morannon is a diversion intended to draw Sauron’s attention away from Frodo and Sam, who are secretly approaching Mount Doom.
Morannon should not be confused with Minas Morgul, the former city of Minas Ithil, or with Cirith Ungol, the pass and tower associated with Frodo’s route. “Mordor” names the entire region, whereas Morannon identifies one specific entrance. The word is commonly translated as “Black Gate” from Tolkien’s Sindarin vocabulary.