Chief executive Ivan Gazidis will leave Arsenal on 31 October to take up a similar post at AC Milan, the Premier League club have announced.
Speculation that Gazidis - who oversaw Unai Emery's appointment to replace Arsene Wenger in May and has also been behind the change in management structure at the Emirates Stadium - will depart for Italy has been rife for some time.
Now the move has been confirmed, with Raul Sanllehi, currently head of football relations at the Emirates Stadium, to become head of football when Gazidis heads to Milan.
Meanwhile Arsenal's chief commercial officer Vinai Venkatesham will take over the role of managing director at the same point.
Gazidis, 54, has worked for the Gunners since 2009 and played a major role in introducing roles such as Sanllehi's, as well as that of head of recruitment - held by Sven Mislintat.
Those appointments wrestled some power away from Wenger, whose 22-year tenure came to a close at the end of last season.
Emery has since taken the reins after a thorough interview process headed up by Gazidis, who will now leave to fulfil a similar role at San Siro.
Raul Sanllehi and Vinai Venkatesham appointed head of football and managing director respectively, as Ivan Gazidis leaves for A.C. Milan— Arsenal FC (@Arsenal) September 18, 2018
The changes behind the scenes at Arsenal in recent months have been vast, with majority shareholder Stan Kroenke last month launching a bid to take overall control of the club through his company Kroenke Sports and Entertainment (KSE).
His son, Josh Kroenke, is deputy chairman of KSE and praised the work of Gazidis during his tenure at Arsenal.
"It has been a pleasure working with Ivan. We will miss the wisdom, insight and energy he brought to our club on a daily basis over the past decade," he said in the statement announcing Gazidis' departure.
"We are confident we have outstanding people in Raul and Vinai, and we look forward to working with them and coach Unai Emery to continue to move the club forward on and off the pitch."