East Midlands Ambulance Service (EMAS) chief executive Phil Milligan is leaving the organisation after nearly two years in the role.
Jon Sargeant, director of finance and performance, will take his place until a successor is appointed.
News of his exit comes just weeks after EMAS was fined £3.5m after it missed national targets for patients involved in life-threatening emergencies for the third successive year.
The target is to get to 95 per cent of cases within 19 minutes, but EMAS only achieved 91.85 per cent.
Under Mr Milligan’s leadership, EMAS approved plans to replace 65 ambulance stations with nine superhubs, 19 stations and more than 100 community points.
Jon Towler, chairman of the EMAS Board, said: “Phil led the organisation through a time of significant change. He leaves EMAS in a considerably better shape and with a clear plan for the future.
“The whole board extends its thanks for the improvements made and wishes him well for the future.”
As EMAS chief executive, Mr Milligan established the Being the Best plan to improve the service for patients in the region.
Mr Milligan said: “I joined EMAS to make a difference. With the plans in place and progress made I am proud to leave EMAS in a much stronger position.
“I am looking forward to spending more time with my family.”