The Limlight was a river at the north of Rohan that ran through northern Fangorn and emptied into the Anduin.
It formed the southern boundary of the Field of Celebrant, and was claimed by Celeborn and Galadriel of Lothlórien as the southern boundary of their realm. It was also the historic northern border of Gondor, and later of Rohan.
In T.A. 2510 the Northern Army of Gondor had been driven by the Balchoth and Orcs across the Limlight. The men of Gondor were facing destruction when Eorl the Young, leading the Éothéod, fell upon the rear of the enemy and drove them southward with heavy losses over the Limlight into the Wold.
Aragorn, at the behest of Gandalf, hunted and captured Gollum in 3017; on his journey north to Thranduil they crossed the Limlight since Aragorn was taking a route west of the Great River.
In February 3019 the Fellowship of the Ring floated past the mouth of the Limlight as they headed south upon the Anduin.