The River Calder is a river in West Yorkshire, in Northern England. The Calder rises on Heald Moor in Lancashire close to the source of another river with the same name, and then flows east into West Yorkshire through green countryside, former woollen-mill villages and towns before joining the River Aire near Castleford. The river itself is only navigable in short sections, but these sections are connected by artificial "cuts" (e.g. Horbury Cut) to form the Calder and Hebble Navigation, a popular leisure waterway which is part of the connected inland waterway network of England and Wales.