The River Clyst is a river of Devon, England. The name derives from Old English, and translates as Clean-stream (the Welsh name of Clydach, has similar origins). The river lends its name to several settlements on its route, Clyst Honiton, Clyst St Lawrence, Clyst St George, and Broadclyst. The William part of Clyst William derives from the Old English of aewelm, which means river source.