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. It 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.