In J. R. R. Tolkien's fictional universe of Middle-earth, the river Bruinen or Loudwater is a river which appears in The Hobbit as well as The Lord of the Rings.

The Bruinen began with two tributaries in the Misty Mountains, one of them was began at the High Pass where Goblin-town was later dug.

The river formed the southern border of the Kingdom of Arnor and later the petty-realm of Rhudaur, south of it lay Eregion or Hollin.

The southern arm of the Bruinen flowed through the deep valley where Elrond founded the refuge of Imladris or Rivendell. Elrond had some control over the river.

The Bruinen had only one point where it could be passed, a Ford near Rivendell. This Ford and by extension the river were called the Edge of the Wild.

When Thorin Oakenshield and company went to reclaim Erebor, they passed the Bruinen after their adventure with the Trolls, before they long paused at Rivendell.

At the beginning of the War of the Ring Frodo Baggins was raced on Glorfindel's horse towards the Ford of Bruinen, with the Ringwraiths in hot pursuit. At the Ford Frodo, poisoned by a deadly wound, made his stand, and defied the Witch-king of Angmar. This lured the Ringwraiths into the Bruinen, and Elrond and Gandalf the Grey released a great flood, which took the form of horses made out of water due to Gandalf's magic. This flood killed the horses of the Ringwraiths and their physical forms, buying the Fellowship of the Ring some time.