Dennis Flanagan (July 22, 1919, New York City – January 14, 2005, New York City) was the founding editor of the modern Scientific American magazine. In 1947, Flanagan, Donald H. Miller, Jr. and Gerard Piel, under the leadership of Piel, acquired and reorganized the then 102-year-old Scientific American.Flanagan was the editor of Scientific American for more than 37 years starting in 1947.