Barbara Frost, chief executive of WaterAid, has announced that she will retire next year.
Frost, who turns 64 in October, will have led the charity, which provides water, sanitation and hygiene in 37 developing countries, for 11 years.
A statement from the charity said that under Frost’s guidance it had tripled its annual income to £86m.
It said she had also led the transformation of WaterAid from a UK-based international NGO to a global federation with members in countries including Australia, Japan, India and the US.
A spokeswoman for the charity said it had not yet been decided when in 2017 Frost would leave, but it was expected to happen between April and July. She said the charity expected to begin the recruitment process for a successor in September this year.
Frost said in a statement: "This has been a very hard decision, to leave such a wonderful team and an organisation that is focused on transforming lives.
"I will be 65 next year and would like to have more time with my partner Keith to travel and to do new things."
She said that 2017 was also an appropriate time in the cycle of the charity’s global strategy for her to hand over the reins.
Tim Clark, chair of WaterAid UK, said: "We wish we could keep Barbara forever. She is such an inspiration to us all, leading WaterAid with vision, calm pragmatism and humility.
"Barbara always selflessly puts people first, whether it’s the people we work for to help transform their lives, the people who support us, or the people who work for WaterAid. We will miss Barbara hugely – but are pleased that she is putting herself and her partner Keith first."