The Rossendale Valley also known as the Forest of Rossendale, is an upland area of North West England, in Lancashire. The area is within the Borough of Rossendale. It consists of the steep-sided valleys of the River Irwell and its tributaries, which flow from the Pennines southwards into Greater Manchester and cut through the open unwooded moorland, which is characteristic of the area, despite the ancient designation of "forest".