In J. R. R. Tolkien's fictional universe of Middle-earth, Ossiriand was a region of eastern Beleriand.

Ossiriand, or Land of Seven Rivers, was the most eastern region of Beleriand during the First Age, lying between the Ered Luin and the river Gelion.

The Seven Rivers were, from north to south:

1. River Gelion
2. River Ascar or Rathlóriel
3. River Thalos
4. River Legolin
5. River Brilthor
6. River Duilwen
7. River Adurant

Along the northern shore of the Ascar ran the Dwarf-Road to Nogrod.

Ossiriand was a green and forested land, and it was not populated by the Sindar. In the early First Age before the rise of the Moon, a part of the Telerin Elven people called Nandor entered Ossiriand under their leader Denethor, and were given permission by Thingol to settle the lands.

After them the land was often renamed Lindon, for The Singers, after the old clan-name of the Telerin which the Nandor still used in their tongue. They became known as the Laiquendi, or Green-Elves.

After their leader Denethor was killed in an Orc-raid they chose no more leaders, and many of them removed to Doriath.

North of Ossiriand lay the land of Thargelion, and south of the river Adurant later lay the Land of the Dead that Live, where Lúthien and Beren lived their second lives.

Ossiriand was the only part of Beleriand that survived the War of Wrath, but Belegaer the Great Sea broke through the mountain chain at the former riverbed of Ascar, creating the Gulf of Lhûn. In the Second Age and Third Age the former lands of Ossiriand and Thargelion were known as Lindon, where Rodnor Gil-galad and Círdan ruled.