The Mardyke (sometimes, but less frequently, Mar Dyke, occasionally Mardike) is a small river, mainly in Thurrock, that flows into the River Thames at Purfleet, close to the Queen Elizabeth II Bridge. In part, it forms the boundary between the Essex hundreds of Barstable and Chafford. The river gives its name to the Mardyke Valley—a project aimed at increasing appreciation and usage of recreational land around the Mardyke.