Stewart Milne has stepped down from the role of Aberdeen chairman to be replaced by US-based businessman and current vice-chairman Dave Cormack.
The move comes as part of new investment and a 'strategic partnership' with Atlanta United, the US Major League Soccer Club.
Building tycoon Milne will officially leave after the club's December AGM along with Aberdeen Chief Executive Duncan Fraser and directors Ian Jack, Duncan Skinner and Craig Brown.
On the announcement, Milne declared Cormack as the natural choice to succeed him following 22 years at the helm.
Milne said: "For four years, we've been working on a succession plan. It's been no easy task to find the right person who is willing to take on the onerous role of chairman, with responsibility for both the financial health and growth of the club.
"In bringing Dave (Cormack) onto the Board and then appointing him vice-chairman, we viewed him as the natural successor.
"He qualifies on both counts. He is prepared to take on the commitment and has already proved his ability to secure significant new investment. Importantly, he is passionate about Aberdeen and the club."
Since June 2017, Cormack has delivered £11.2m of new investment, including £1.4m for the Aberdeen FC Community Trust, and, on taking control, he will front a further £5m of investment which will provide working capital for the club's day-to-day operations.
And with recent completion of a new £12m training ground, combined with strong football and commercial performance, Milne believes it is the ideal time to step aside as chairman.
He added: "I have always said I would relinquish the reins when the right opportunity arose and I believe that time has now come. I'm proud to have had the opportunity to lead the club I love for over two decades.
"We have been in a consistently healthier position for several years now and I'm pleased to be able to hand the club over to safe hands in the knowledge that we are debt-free and have more than doubled revenues from around £7.8m in 2013 to almost £16m today."
Atlanta United are owned by billionaire Arthur Blank, who is also the owner of the Atlanta Falcons in the NFL with the new investment coming from Cormack and his group of investors, including Tom Crotty, Roger Lee and now AMB Sports & Entertainment (parent company of Atlanta United).
The latter, AMB Sports and Entertainment, will take up to 10 per cent stake in Aberdeen, and invest £2m into the club.