The Borough of Colchester is a local government district and borough in Essex, England, named after its main town, Colchester. The borough covers an area of 125 square miles (320 km²) and stretches from Dedham Vale on the Suffolk border in the north to Mersea Island on the Colne Estuaryin the south.

The borough was formed on 1 April 1974 by the merger of the former borough of Colchester, covering an area of around 17.7 square miles (46 km²),[1] with the urban districts of West Merseaand Wivenhoe, along with Lexden and WinstreeRural District.