The River Winster is a river in the English county of Cumbria. The Winster was the boundary between the historic counties of Lancashire and Westmorland. It has a relatively small catchment area; other streams flow parallel to it on either side.
The Winster is about 20Â km or 12 miles long, and rises about 2Â km south of Bowness-on-Windermere, between the hamlets of Winster and Storrs (the latter is on Windermere) and follows a southerly course, flowing past the settlements of Ludderburn, Hartbarrow and Bowland Bridge, before it is joined by Arndale Beck at Bridge House.