Keswick takes over from Peter Hill-Wood, 77, who has decided to leave the board after suffering a heart attack last year. Hill-Wood had been at the helm since 1982 and his father Denis and grandfather Samuel ran the club before him in a family dynasty stretching back to 1927.
Hill-Wood said: “This has been a difficult decision as Arsenal has been a huge part of my life.”
Keswick — full name Sir John Chippendale Lindley Keswick — is an old Etonian and director of such firms as DeBeers and Investec Bank. Arsenal majority owner Stan Kroenke said: “He has a respected track record in business and will provide further direction and support in our ambition to compete at the top of the game.”