The Water Services Regulation Authority, or Ofwat, is the body responsible for economic regulation of the privatised water and sewerage industry in England and Wales. Ofwat's main statutory duties include protecting the interests of consumers, securing the long-term resilience of water supply and wastewater systems, and ensuring that companies carry out their functions and are able to finance them.

Ofwat primarily sets limits on the prices charged for water and sewerage services, taking into account proposed capital investment schemes (such as building new wastewater treatment works) and expected operational efficiency gains. The most recent review was carried out in 2014; reviews are carried out every five years, with the next due to take place in December 2019.

The Water Act 2014 extended retail competition to all non-household customers of English water companies from April 2017 and provided for possible future competition in wholesale markets. Ofwat's role includes regulating such water and wastewater markets and promoting effective competition wherever appropriate.

Ofwat consists of a board, plus an office of staff which carries out work delegated to them by the board.

The Environment Agency is responsible for environmental regulation, and the Drinking Water Inspectorate for regulating drinking water quality. Water in Northern Ireland is regulated by the Northern Ireland Authority for Utility Regulation, and the supply and treatment is carried out by the government-owned Northern Ireland Water. There is no separate charge for water for residents or companies in Northern Ireland. Instead, water is paid for by the rates system. The water industry regulator in Scotland is the Water Industry Commission for Scotland.