Chelsea have announced chief executive Ron Gourlay is leaving the club after 10 years working at Stamford Bridge.
Gourlay, who previously worked for Manchester United, succeeded Peter Kenyon as chief executive in 2009.
"I feel the time is right to move on to other challenges," Gourlay said in a statement on the club website.
Chairman Bruce Buck and director Marina Granovskaia will take on Gourlay's responsibilities until "additional appointments" take place.
Since the arrival of Roman Abramovic in 2003, only Trevor Birch, Kenyon - who this week took up an advisory position at Atletico Madrid - and Gourlay have held the chief executive position at Chelsea.
In that time frame, the Blues have become established as one of the powers of European football, winning three Premier League titles and the Champions League in 2012.
Gourlay called it a "privilege" to have been involved in the club's successes on and off the pitch since his arrival in 2004 and thanked Abramovich and other directors for their support.
"Ron's efforts have helped the club to achieve its position as one of the leading football clubs in the world," added the club in a statement.
|Hired during Gourlay's reign as chief executive|
|Andre Villas-Boas||June 2011|
|Roberto Di Matteo||March 2012|
|Rafael Benitez||November 2012|
|Jose Mourinho||June 2013|
As chief executive, Gourlay was at the helm when the Blues recorded their first annual profit of the Abramovich era in 2012.
He was involved in the controversial interim appointment of Rafael Benitez as manager in the same year, as well as the return of Jose Mourinho for a second spell as manager in 2013.
Carlo Ancelotti, Andre Villas-Boas and Roberto Di Matteo also worked under him during their time with the current Premier League leaders.
Gourlay also oversaw Chelsea's three record signings during his time as chief executive as they paid £50m for Fernando Torres in 2011, £32m for Eden Hazard in 2012 and the same figure for Diego Costa in July.