The chief constable of Thames Valley Police is leaving the force in April next year.
Sara Thornton is to become the chair of the new National Police Chiefs’ Council, a newly created body which represents senior police officers.
Ms Thornton, who was appointed chief constable in April 2007, said she was leaving with a “heavy heart”, but felt it was right time to “face a new challenge”.
She said: “I have been with Thames Valley Police for 14 years and so it is with a heavy heart that I will be leaving the force.
“I could happily stay here, but there is a sense of which it is time to move on and face a new challenge.
“I will be genuinely sad to leave such a fantastic force and such a wonderful group of people, and will miss serving the public of the Thames Valley.”
Following an announcement two weeks ago that the force faced cuts totalling £45million, Ms Thornton said the next three years would be “challenging”, but remained confident it would not impact on front-line services.
She added: “Having been formally offered the position of Chair for the National Police Chiefs’ Council, I look forward to leading this new body and influencing policing at a national level.”