Sunderland chief executive Peter Walker has resigned after 10 years with the club.
Walker, who has been chief executive since 2004, will formally step down towards the end of the year.
"I am leaving the club in an excellent position but think the time is right for me personally to broaden my horizons and accept a challenge in a new industry,'' said Walker.
Sunderland chairman Niall Quinn said: "We successfully talked Peter out of leaving about 18 months ago as I really needed him to help us during the important and transitionary period after the takeover of the club by Drumaville.
"I have had to reluctantly accept his decision on this occasion but for the record, although he is not one to look for credit, I think supporters should know of the important work he has done behind the scenes for this club.''