The Aire and Calder Navigation is a river and canal system of the River Aire and the River Calder in the metropolitan county of West Yorkshire, England. The first improvements to the rivers above Knottingley were completed in 1704 when the Aire was made navigable to Leeds and the Calder to Wakefield, by the construction of 16 locks. Lock sizes were increased several times, as was the depth of water, to enable larger boats to use the system.