Dŵr Cymru Welsh Water is a not-for-profit company that supplies drinking water and wastewater services to most of Wales and parts of western England that border Wales. In total, it serves around 1.4 million households and businesses and around three million people – and supplies nearly 830 million litres of drinking water per day.

It is regulated under the Water Industry Act 1991 as amended by the Water Act 2014

Welsh Water originated from the privatisation in 1989 of water supply and wastewater arms of the Welsh Water Authority which itself had its origins in the Welsh National Water Development Authority that was created by the 1973 restructuring of the water industry in England and Wales.

Welsh Water Authority was privatised by stock market flotation in 1989, along with the other nine regional water authorities, which provided the company with a substantial cash surplus for some years, which is used to diversify in a wide range of sectors including leisure (Hotels, Fishing etc.). It renamed itself, Hyder, in 1996 after taking over a local electricity company (SWALEC) and becoming a water and electricity multi-utility.

However, in 1999/2000, following the Windfall Tax on utility profits and the 1999 Ofwat price review, Hyder got into financial difficulties which led to its breakup following a takeover battle. Western Power Distribution purchased Hyder on 15 September 2000 with a view to acquiring its electricity distribution business and rapidly sold off Hyder’s other assets. Dŵr Cymru Welsh Water was sold, along with £1.85 billion of Hyder debt, for £1 by WPD to Glas Cymru, a company set up by Nigel Annett and Chris Jones with the support of the company’s first chairman Lord Burns to run the company for public benefit. Under the terms of its licence, Glas Cymru, a company limited by guarantee, may not operate in sectors other than water.