The Thames Conservancy (formally the Conservators of the River Thames) was a body responsible for the management of that river in England. It was founded in 1857 to replace the jurisdiction of the City of London up to Staines. Nine years later it took on the whole river from Cricklade in Wiltshire to the sea at Yantlet Creek on the Isle of Grain. Its territory was reduced when the Tideway (upper and lower estuary) was transferred to the Port of London Authority in 1909.
In 1974 the conservancy was taken into the Thames Water Authority, later to devolve to the Environment Agency in almost all respects.