Peter Hill-Wood stepped down as Arsenal chairman with Sir Chips Keswick taking his place, the club announced.
Peter Hill-Wood, who was the chairman since 1982, stood down from the board for health reasons and is recovering following a heart attack last year.
"This has been a difficult decision as Arsenal Football Club has been a huge part of my life," he told the club's official website. "Although I am feeling better I feel this is the right time for me to stand down.
"I would like to thank our majority owner, Stan Kroenke, for the respectful and dignified way he has handled this and I know Sir Chips is the right person to take the club forward."
Kroenke said Hill-Wood will be missed by Arsenal, while welcoming the appointment of Keswick.
"Peter has been a wonderful custodian of this club," he said. "He has been a member of the Arsenal board for 51 years and his vision and steadfastness have been central to the successes of this great Club over that time.
"Peter will be sorely missed but we will ensure we recognise his many contributions to the Club in an appropriate way."
"I am delighted that Sir Chips has agreed to become chairman. He has a well respected track record in business and he will provide further direction and support in our ambition to compete at the top of the game here and in Europe and to win trophies."
The 73-year-old Keswick has been a part of the Arsenal board since 2005. "Firstly, I am sad to see Peter standing down due to his health and we all hope he continues well in his recovery," Cheswick said. "The Hill-Wood family has made an extraordinary contribution to Arsenal over many decades. They have been central to the Club's many achievements during this time.
"I am greatly honoured to have been appointed chairman of Arsenal Football Club. This is one of the great clubs in the game, recognised and loved by millions. I am looking forward to leading the Club to future success."
