Lefnui was the westernmost of the many rivers of southern Gondor, the Lefnui rose in the far west of the White Mountains. It followed an erratic course through the lands west of the hills of Pinnath Gelin, until it emptied into the Bay of Belfalas through a long narrow firth. This river formed the eastern boundary of the Drúwaith Iaur.
The Lefnui played little part in history, though it was remembered by the Men of Rohan. When the Dunlendings invaded Rohan in T.A. 2758, they were aided by Gondor's enemies from the south. These sea-going marauders landed at Lefnui's mouth on their mission to overrun and destroy the Rohirrim, though they would eventually be defeated.
Other versions of the legendarium
- J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "The West of Middle-earth at the End of the Third Age" [map]
- J.R.R. Tolkien, Christopher Tolkien (ed.), Unfinished Tales, "The Drúedain", p. 384
- J.R.R. Tolkien, The Lord of the Rings, Appendix A, "The House of Eorl"
- J.R.R. Tolkien, "The Rivers and Beacon-hills of Gondor" (edited by Carl F. Hostetter), in Vinyar Tengwar, Number 42, July 2001, p. 14
- J.R.R. Tolkien, Christopher Tolkien (ed.), The War of the Ring, "Part Three: Minas Tirith", "XIV. The Second Map", West, p. 434