Southern Water is the utility responsible for wastewater collection and treatment in Hampshire, the Isle of Wight, West Sussex, East Sussex and Kent, and for water supply and distribution in the approximately half of this area.
Some areas within the Southern Water region are supplied by a number of smaller water supply companies.
It is regulated under the Water Industry Act 1991.
The Water Act 1973 resulted in the formation of the Southern Water Authority (SWA), taking the responsibility away from the local authorities.
Nevertheless, the SWA maintained a regional management approach, retaining three separate regional headquarters.