Arsenal managing director Keith Edelman is leaving the club "in search of a fresh challenge", the club revealed to the Stock Exchange this morning.
Edelman has spent eight years at the club and oversaw the move to the Emirates Stadium from Highbury.
He has resigned as a director of Arsenal Holdings PLC but "will be retained by the club for a 12-month period to ensure that a smooth transition takes place".
Arsenal have already started the search for Edelman's successor, with director Ken Friar - who held the role for 18 years until 2000 - assuming the role of acting managing director.
Edelman said: "I have thoroughly enjoyed my time at Arsenal.
"It has been a very exciting period for the business and I am proud to have contributed to the club's many off-field achievements over the past eight years, not least the Emirates Stadium project. Now that we have completed our second season at Emirates, I believe it is the right time to seek pastures new and embark upon fresh challenges."
Gunners chairman Peter Hill-Wood expressed a "debt of gratitude" to Edelman.
"Keith has played a major role in the growth of the club since he joined in 2000," he said.
"In that time we have successfully implemented the move from Highbury to Emirates Stadium that has underpinned the future of the business and confirmed our position as one of Europe's leading clubs. We are grateful to Keith for his crucial role in this transformation.
"Under Keith's stewardship the club has achieved record profits and the board owes him a debt of gratitude for his contribution.
"We wish him the very best for the future."
The statement from Arsenal Holdings PLC said: "The board has already initiated the search for a new managing director and will update shareholders and stakeholders when appropriate.
"In the meantime, director Ken Friar, who has a wealth of football-based experience and business acumen having previously occupied the role of managing director (1982-2000), will assume the position of acting managing director."