Lebennin was a region and fiefdom in southern Gondor.
Known as Fair Lebennin of the Five Streams, referring to the Five Rivers of Lebennin, Lebennin was one of the faithful fiefs of Gondor, and one of its provinces. It was a wide green land that lay between the rivers Gilrain and Anduin and the lower reaches of Erui. The Anduin delta lay to the South and the White Mountains lay to the North. Pelargir was it's chief city. Linhir was another town or city within it.
Lebennin was largely populated by Men of mixed blood, as many Men of Lebennin traced their ancestry to the forgotten 'Men of the Mountains' that had been displaced from the White Mountains by the Númenóreans.
During the War of the Ring, Lebennin was under attack by the Corsairs of Umbar, and so could not send many men to the aid of Minas Tirith. Lebennin was rescued by Aragorn and his Army of the Dead, spirits of the Oathbreakers of Dunharrow.