The Forest River was a river of Rhovanion. It ran approximately two hundred miles in length that ran from the Grey Mountains in Rhovanion through the northern portion of Mirkwood forest and through the mountains of Thranduil's underground realm, before joining the River Running at the Long Lake. The Enchanted river in Mirkwood flowed into the Forest River about ten miles before (west of) the Elven-king's Halls.