|Location||Meeting of Udûn and Gorgoroth, joining of spurs of Ered Lithui and Ephel Dúath|
|Etymology||S. carach "jaws" + angren "iron"|
Carach Angren or Isenmouthe was a pass in the northwest of Mordor.
The pass was formed where spurs reaching out from the ranges of the Ephel Dúath and the Ered Lithui met, leaving only a narrow passage between the Plateau of Gorgoroth and the smaller valley of Udûn to the north.
As the passage to the Black Gate of the Morannon, Carach Angren was heavily fortified, and both the rocky spurs that overlooked it carried fortresses and watchtowers. Across the passage itself, a wall of earth had been built, and a great ditch had been dug across the opening spanned by a single bridge.
Both Carach Angren and Isenmouthe mean "Iron-mouth": "It was so called because of the great fence of pointed iron posts that closed the gap leading into Udûn, like teeth in jaws."