She has worked at the pub company and brewer for the past 10 years and will step down from her role to pursue other interests.
Bosher joined Greene King, from JJB Sports, as operations director of its local pubs division in April 2013, taking on her current role in February 2020.
Commenting on her departure on LinkedIn, Bosher said: “After 10 glorious and very successful years I have made the decision to leave Greene King. I’ve had the most wonderful journey and the happiest of times.
“I’m very satisfied that I leave behind me a great team across Urban, Crafted, Metro and Hotels who will continue to push the idea of what Greene King can be for the future. I am forever grateful to the pubs and their teams for their support and hard work.
“I’m very much looking forward to the future and a fresh challenge after a rest and some family time.”
Nick Mackenzie, CEO of Greene King, said: “Karen has played a pivotal role during her 10 years at Greene King, including setting up and leading our Premium, Urban and Venture Brands division and I would like to thank her for her dedication and contribution to the business.
"She has been a key part of the team that has delivered strong progress and change, and we wish Karen all the best for the future.”