Sunderland have confirmed that former chairman Niall Quinn has left the club with immediate effect.
The North East club have announced the departure of the 45-year-old, who has been part of the Black Cats hierarchy for six years, which included a five-year stint as chairman and brief appointment as manager.
The former striker has stepped down from his role within the club for personal reasons and is expected to move back to Ireland to be with his family.
"I've had the most amazing six years and it gives me a huge sense of pride to see where Sunderland is today," Quinn told the club's official website. "Sunderland is in an incredibly fortunate position to have a hugely talented team of people leading the football club right now.
"There is a tremendous amount of energy about the place and the Board and the executive management team are a dynamic and committed group, who hold the best interests of the club at the core of all they do. Everything is in place for Sunderland to really make a statement, which was always my aim.
"From a football perspective, securing the services of Martin O'Neill has been an absolute highlight. In Martin we have a man that understands the region, the club and the unique place it holds in the lives of its supporters and I am confident that he will harness the immense passion that exists here and take us to new heights."
Club chairman Ellis Short added: "Niall Quinn is and always will be a Sunderland legend. His vision brought me into the club and that vision still inspires what we do.
"He has been a trusted friend and advisor to me throughout our time together at Sunderland and whilst I'm sad about his departure, I respect his view that his 'work is done'. My job is to carry on that work.
"He has been a wonderful servant to Sunderland and his determination to see the club grow has been inspirational."
Quinn stepped down from his role as chairman last October.