The Lhûn, or Westronized Lune, was a river of north-western Eriador. It gave its name to the Gulf of Lune and the Mountains of Lune. Of old, the Lhûn had been a line of defence: first against Sauron, and later against the Witch-king.
Geography
The Lhûn found its origin in the First Age or before. The river had its sources in the far north of the Blue Mountains, and had two tributaries: the Little Lune and an unnamed river that had its origin in the Emyn Uial.
Its original course is no longer recorded in history, but following the War of Wrath, its course was severely altered; after the breaking of the Blue Mountains, it flowed in the newly-formed Gulf of Lune.
In the Second Age, the Lhûn formed the border between eastern Lindon and Arnor. Elendil's people dwelt about the courses of the Lhûn. During Sauron's advent, Gil-galad and Elendil were desperately protecting the Grey Havens, and managed to hold the Lhûn.
During the War with Angmar, it formed the end of the Witch-king's influence: many of the Dúnedain fled across it. When Eärnil II came, passage was won back over it. With their defeat imminent, many of the Witch-king's minions drowned in the river Lhûn.