Hadleigh is a town and former civil parish, in the borough of Castle Point, in southeast Essex, England, on the A13 between Thundersley, Benfleet and Leigh-on-Sea with a population of 18,300. It has a squared bypass to the north.

Castle Point is a local government district with borough status in south Essex, England, lying around 30 miles (48 km) east of London. The borough comprises the towns of South Benfleet, Hadleigh and Thundersley on the mainland, and the adjoining Canvey Island in the Thames Estuary, which is connected to the mainland by bridges.