Arsenal have appointed Chips Keswick as chairman of the club after Peter Hill-Wood stood down for health reasons.
Hill-Wood joined the board in 1962 and followed in his father and grandfather's footsteps, who were also chairman of the London side.
But after suffering a heart attack last year, he has taken the decision to resign his position.
"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."
Keswick has been a member of the Arsenal board since 2005 and will work towards securing the club's long-term ambitions.
He added: "Firstly, I am sad to see Peter standing down due to his health and we all hope he continues well in his recovery.
"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."
Majority owner Kroenke paid tribute to the departing Hill-Wood and welcomed Keswick to the role.
"Peter has been a wonderful custodian of this club," he commented.
"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.
"I am delighted 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."