The River Len is a river in Kent, England. It rises at a spring in Bluebell Woods to the southeast of the village centre of Lenham 0.6 miles (0.97 km) from the source of the River Great Stour; both rise on the Greensand Ridge. Its length is c10 miles (16 km). It enters the River Medway at Maidstone. The river powered a number of watermills on itself and its tributaries in the parishes of Ulcombe, Leeds, Hollingbourne, Boxley and Maidstone.