The Gladden (called Sîr Ninglor "River Goldwater" by the Elves) was a short but important river of the Vales of Anduin.
The source of the river begun as two unnamed arms in the central Misty Mountains, near an important pass. It then flowed eastwards to the Great River Anduin, which it met in a series of marshes called the Gladden Fields.
After the Last Alliance of Elves and Men, Isildur, heir of Elendil and bearer of the One Ring, was assailed by Orcs near the Gladden Fields, and the One Ring was lost here in the Gladden river.
Much later during the Third Age some Stoors lived near the streams of Gladden, and from them came Déagol who found the ring, and was killed by Sméagol (Gollum), who long held the Ring. Gollum eventually followed the stream up to its source, ending up in forgotten caves near Goblin-town.
Saruman searched the Gladden extensively during his search for the Ring, but never found the ring, although he seems to have found Isildur's remains.
In T.A. 3018 some of the scouts sent out by Elrond after the arrival of the hobbits in Rivendell crossed the Misty Mountains over the pass at the source of the Gladden to seek the wizard Radagast at Rhosgobel, but he was not at home, and they returned through the Dimrill Dale.
Gladden (From Old English glædene) is another name for the "flag" or "iris", now usually spelt gladdon.
Sîr Ninglor is a Sindarin name meaning "River Water-gold", apparently consisting of sîr ("river"), nîn (pl. of nen ("water") + glaur ("gold").
The Gladden flows east from the Misty Mountains, crashing through the dwarve ruins of Kidzul-kâlah in the form of a waterfall.
Beyond the fall, the haunted Gladdenmere fills the upper valley.
The Gladden Falls pour down from the lake into the extensive marshland below.
Known as Gladden Fields, they, along with the river, lake, and falls, take their name from the thousands of yellow gladdens growing in the watery fens.