Danielle Oum will step down from the post at the end of February 2021, to take up a new role as Chair of Birmingham & Solihull Mental Health NHS Foundation Trust.
Ms Oum took up the post in 2016 and is credited with guiding the trust out of special measures, forming a more stable and diverse trust board, and rooting out inequality.
She also played a key role in the evolution of Walsall Together.
Ms Oum, who is also chair of the whg Housing Association, said she would "always feel a tremendous sense of pride" in having chaired the trust.
Trust chief executive Richard Beeken said he was "understandably saddened" to lose Ms Oum and wished her well in her new role.
The trust says details of the new chair will follow in the coming weeks.