Irving Kahn (December 19, 1905 – February 24, 2015) was an American investor and philanthropist. He was the oldest living active investor. He was an early disciple of Benjamin Graham, who popularized 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.