thumb|right|County Lock, looking downstream. Brewery Gut is entered under the bridge in the distance.
thumb|right|The lower lock gates, with the river in a state of flood. The old brewery stable block can be seen.
thumb|right|County Lock in 1975 with Simonds' Brewery in background.
County Lock is a lock on the River Kennet in Reading town centre in the English county of Berkshire. It is now administered by the Canal & River Trust as part of the Kennet and Avon Canal. Downstream from the lock is Brewery Gut, a particularly fast flowing, narrow and dangerous stretch of the river.
County Lock has the lowest rise of the locks on the Kennet, as boats only rise or fall about 30 cm (1 foot) in the lock. The main stream of the Kennet flows down the weir on the far side of the lock, while another arm of the Kennet disappears under the Bridge Street Roundabout.
The first County Lock was built between 1718 and 1723, during the navigation works undertaken under the supervision of the engineer John Hore of Newbury in order to create the Kennet Navigation between Reading and Newbury. Initially the lock was located on the north side of the river, adjacent to Bear Wharf, but it was relocated to its current location on the south bank as part of the Reading waterworks improvement scheme of 1876.