Canvey Island is a town, civil parish and reclaimed island in the Thames estuary, near Southend-on-Sea, in the Castle Point district, in the county of Essex, England. It has an area of 7.12 square miles and a population of 38,170. It is separated from the mainland of south Essex by a network of creeks. Lying only just above sea level, it is prone to flooding at exceptional tides and has been inhabited since the Roman conquest of Britain.