River Blackwater, Essex

The River Blackwater is a river in Essex, England. It rises as the River Pant in the northwest of the county, just east of Saffron Walden, and flows in a generally southeast direction to Bocking, near Braintree, via Great Sampford and Great Bardfield. At Bocking, it becomes the River Blackwater, and veers east to flow past Bradwell Juxta Coggeshall and Coggeshall. It then veers south, flowing past Kelvedon and Witham, before reaching Maldon. There, it veers east again and empties into the Blackwater Estuary, which in turn meets the North Sea at Mersea Island.

The River Blackwater has two major tributaries: the River Brain, which meets it just south of Witham, and the River Chelmer, which meets it just east of Maldon. The lower reaches of the Chelmer, from Chelmsford, were canalised in the 1790s, and the navigation diverts water north of the Blackwater through Maldon before emptying into the Blackwater Estuary at Heybridge Basin.