Cumbria CC chief executive Peter Stybelski is stepping down from the post to take early retirement on the grounds of ill health.
Mr Stybelski, who underwent a kidney transplant in March 2007 and has been advised by doctors to step down, will leave his post on 28 August.
The council said recruitment for a successor will begin “as soon as possible”. Corporate director for adults & culture, Jill Stannard, will remain in the role of acting chief executive in the interim.
Mr Stybelski described the move as “one of the hardest decisions I have ever made” describing Cumbria as “a wonderful county with passionate people and limitless potential”.
He added: “I owe it to myself and my family to put my long-term health first.
“Many people will be aware that I have been away from work since February this year - and I have reached the stage where I have to accept that it is not possible to find the right balance between my enthusiasm for the job and the need to look after my health.”
“I have made many friends here, and met so many dedicated colleagues who share my commitment to providing excellent public services. I am very proud to have worked with them all.”
Council leader, Jim Buchanan (Con), right, said: “Peter has worked tirelessly for the people of Cumbria, and he has made a huge impact on the county council.
“We have improved our services steadily over the past five years under his guidance, and Peter can look back on his achievements with considerable pride.
“He has earned the respect of all elected councillors, and his sage advice and inspirational leadership will be greatly missed.”