In Kenyon's time at Stamford Bridge, Chelsea won the Premier League twice
Chelsea have announced that Peter Kenyon will be leaving his chief executive role at the end of October.
Kenyon, who left Manchester United in 2003 to join Chelsea, will continue at the Blues as a non-executive director.
The 55-year-old will also continue to represent Chelsea in various capacities, including committee roles with European governing body Uefa.
"I am certain I have at least one major challenge left in me," Kenyon told the club's official website.
"I am extremely proud of my time at Chelsea and of the friendships I have forged with everyone here.
I intend to take a little time off before considering what I do next but I am certain I have at least one major challenge left in me
"I have been in football for 15 years and I can say with great certainty and pleasure the experience at Chelsea is one of the best I have had."
Kenyon left United after three years as chief executive at Old Trafford and had to go on gardening leave before taking up his role at Stamford Bridge at the start of 2004.
Under owner Roman Abramovich, Kenyon took charge of the business side of the club with the long-term aim of becoming one of the most profitable and best supported clubs in the world.
He helped appoint Jose Mourinho as manager in the summer of 2004 and under the Portuguese coach, Chelsea won the Premier League title in 2005 and 2006 as well as the FA Cup in 2007.
Chelsea also reached the Champions League final in 2008, losing to Manchester United on penalties, and won the FA Cup again earlier this year.
"When I joined Chelsea it was an incredible challenge," added Kenyon.
"And together with all the staff, the players, the board and Roman, I think we have really built a club, in a relatively short space of time, that can be in the forefront of European football for many years to come. That is a major achievement.
"I am also delighted that our relationship is not ending and I can continue to make a contribution to keeping Chelsea in that position and to go back to visit friends.
"I intend to take a little time off before considering what I do next but I am certain I have at least one major challenge left in me.
"I would like to wish Chelsea the best of luck for the rest of the season. I am sure the manager Carlo Ancelotti can lead the team to more great things."
Kenyon's time at Chelsea saw success but also controversy.
Sven-Goran Eriksson was linked with a move to Chelsea in 2004 after the Swede was pictured meeting Kenyon while he was still manager of the England team.
In 2005, Chelsea were fined £200,000 for their part in the tapping up affair which saw defender Ashley Cole move to Stamford Bridge from Arsenal.
Without his football knowledge and business acumen Chelsea would not be where we are today
Chelsea chairman Bruce Buck
Earlier this month, Chelsea were banned from signing any new players until January 2011 although they are fighting the decision.
Chelsea were found guilty by Fifa of inducing Gael Kakuta to break his contract with Lens in 2007 but the club have vowed to "mount the strongest appeal possible".
In 2008, Kenyon said the club retained their "ambitious" target of operating profit break even by 2010 but in February this year Chelsea revealed that they made a £67.5m loss for the financial year to the end of June 2008.
Speculation over Kenyon's future at Stamford Bridge surfaced during the summer, with reports linking him with a move to Manchester City.
Chelsea chairman Bruce Buck said: "Peter has done a fantastic job for Chelsea in the last five-and-a-half years and has been absolutely central to the success on and off the field we have had during that time.
"Without his football knowledge and business acumen Chelsea would not be where we are today.
"Everyone at Chelsea thanks him for that contribution and although he will not be with us on a permanent basis, he will have an important role to play as a non-executive director and in the various roles he holds in European football bodies.
"When Peter first joined us we knew we were recruiting a top executive from business generally, not just football. With that always came a certain inevitability he would eventually want to seek a new challenge and I am sure that is what he will do."
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