The chief executive of Ofwat is to step down at the end of August as the embattled water regulator prepares to be abolished.
An interim chief executive is being appointed to replace David Black in due course.
The Government last month announced the regulator would be abolished in a regulatory shake-up that comes as part of its response to public outrage over rising bills, sewage pollution and large bonusses for bosses.
Ofwat may not be formally axed until at least 2027 because the process to overhaul the current system will likely be complex.
Mr Black decided the time is right for him to pursue new opportunities, the regulator said.
Commenting on his decision, Mr Black said: "I have been privileged to be able to lead Ofwat, over the last four years, during which time we have achieved a huge amount together as a team for customers and the environment.
"The 2024 price review backed an investment programme of £104bn, along with a further £50 billion investment in major new water resources, which will improve service, environmental outcomes and resilience in the years to come.
"I wish the team every success as they continue their important work."
Ofwat chair Iain Coucher said: "David has worked, tirelessly, to bring about transformational change in the water sector. He has sought new regulatory powers and resources to hold companies to account, taken major enforcement action and provided funding and incentive packages that drive continual improvements for customers.
"On behalf of the Board and everyone at Ofwat, I would like to thank David for his leadership and his service over the last 13 years and to wish him every success in the future."
Mr Black took over as Ofwat's permanent boss in April 2022, having held the position on an interim basis for the previous 12 months.
He has worked for the water regulator in various roles since 2012.
Water companies are under increasing pressure from Environment Secretary Steve Reed over their award of executive bonuses even as the number of serious pollution incidents has soared.
The UK's biggest water utility, Thames Water, meanwhile, is on the brink of being temporarily nationalised through a special administration regime as it tries to secure a private sector bailout led by its creditors.
