Ormiston Academies Trust chief executive Nick Hudson will retire at the end of this year.
Hudson, who joined the 43-school trust in 2016 as its national director of education, has held the top role for almost six years.
OAT has began recruitment for his replacement. The trust also said Dr Paul Hann, who was chair of trustees until Christmas, will also retire at the end of the academic year.
Hann, a trustee for 11 years, has been replaced as chair by Julius Weinberg, a former chair at Ofsted and deputy chair at Ofqual.