The River Douglas, also known as the River Asland, is a river that flows through Lancashire and Greater Manchester in the north west of England.
It is a tributary of the River Ribble and has itself two tributaries, the River Tawd and the River Yarrow.
At Tarleton, the Douglas is joined by the Rufford Branch of the Leeds and Liverpool Canal.
In 1714 an act of Parliament was passed allowing Robert Holt of Crooke Hall to make the Douglas navigable to small ships.
The river rises on Winter Hill on the West Pennine Moors, and flows for 35 miles through the town centre of Wigan and onto the Ribble estuary past Tarleton, the last 10 miles or so being tidal.
In 1892 the Douglas was diverted in Wigan to the site of Wigan Central railway station.