Mapledurham Lock is a lock and weir situated on the River Thames in England, about 4 miles upstream of Reading. The lock was first built in 1777 by the Thames Navigation Commissioners and the present lock dates from 1908. Despite its name, the lock is located in the Berkshire village and civil parish of Purley-On-Thames on the south bank of the river, rather than in the Oxfordshire village of Mapledurham on the other side of the river. The lock is accessible from Purley village down Mapledurham Drive, a metalled lane that turns to gravel. The weir stretches across the river, in both counties.