Chelsea have announced that Bruce Buck will be stepping down from his role as chairman on 30 June.
The American, who had been in the role since Roman Abramovich became owner in 2003, will continue to support the club as a “senior adviser”.
“Now is the right time to step down and let new ownership build on the strong foundations we have in place,” he said.
“The owners have a compelling vision for Chelsea’s future, and I look forward to helping them achieve it in this new role alongside our incredible staff, players, coaches and supporters.”
Buck added: “I am proud to have helped Chelsea realise great success on the pitch and make a positive impact in the community.”
During Buck’s chairmanship, the Chelsea men’s team claimed 18 major honours and the women’s team won 12.
Co-controlling owner Boehly said that Buck had “led Chelsea Football Club to the highest levels of international and domestic football” and thanked him for “his service and his commitment to the club”.