**Dunham Jackson** (July 24, 1888 in Bridgewater, Massachusetts – November 6, 1946) was a mathematician who worked within approximation theory, notably with trigonometrical and orthogonal polynomials. He is known for Jackson's inequality. He was awarded the Chauvenet Prize in 1935. His book *Fourier Series and Orthogonal Polynomials* (dated 1941) was reprinted in 2004.

Dunham Jackson: *The Theory of Approximation.* AMS, 1930.
Dunham Jackson: *Fourier Series and Orthogonal Polynomials.* Carus Mathematical Monographs, 1941.