Irving Kahn (December 19, 1905 – February 24, 2015) was an American businessman and investor. He was the oldest living active investment professional. He was an early disciple of Benjamin Graham, the creator of the value investing methodology. Kahn began his career in 1928 and continued to work until his death. He was Chairman of Kahn Brothers Group, Inc., the privately owned investment advisory and broker-dealer firm that he founded with his sons, Thomas and Alan, in 1978. Until his death, Kahn performed an active role at the company, though Thomas, who is the firm's president, ran and continues to run the business and was and is still responsible for the firm's investment decisions.