Nivrien was a forest in Cenoriar, inhabited by Limyarin Elves. It was bounded by the rivers Nivril and Taelnen to the north and the river Siril  to the east.
Cenoriar forest

The forest of Nivrien

At first it was ruled by Celepharnír, but after he left to Thalas,the name of its new ruler is unknown. It is possible that the region became part of the royal domain, but it is uncertain.