The Morgulduin was a river of Gondor that began in Morgul Vale in the Ephel Dúath. It ran westward past Minas Morgul until it reached the Cross-roads in Ithilien, where its course turned southwest until it entered the Anduin just south of Osgiliath. Just to the north of the stream was the road from Osgiliath to Minas Morgul. It is probable that the original name of the river was Ithilduin and that it was renamed Morgulduin at the same time Minas Ithil was renamed Minas Morgul after its capture by the Nazgûl.
As Frodo, Sam, and Gollum were approaching the Cross-roads they heard the voice of the river, which sounded cold and cruel. The river was polluted; near Minas Morgul a cold steam issued from the river whose stench and vapours sickened the hobbits.
Other versions of the legendarium
In a note on an earlier map drawn by J.R.R. Tolkien the Morgulduin was called Ithilduin or Duin Morghul.
- J.R.R. Tolkien, The Lord of the Rings, The Return of the King, "Map of Rohan, Gondor, and Mordor"
- J.R.R. Tolkien, Christopher Tolkien (ed.), The Treason of Isengard, "XV. The First Map of The Lord of the Rings", "Maps IIIA and III", p. 312
- J.R.R. Tolkien, The Lord of the Rings, The Two Towers, "Journey to the Cross-Roads"
- J.R.R. Tolkien, The Lord of the Rings, The Two Towers, "The Stairs of Cirith Ungol"
- Association Tolkiendil, "Compound Sindarin Names in Middle-earth", Tolkiendil.com (accessed 3 January 2012)
- Roman Rausch, "2.46 Ithilduin, Duin Morghul", Sindanoorie.net (accessed 26 January 2022)