Donald W. Marquardt (March 13, 1929, New York City – July 5, 1997, New Castle, Delaware) was an American statistician, the rediscoverer of the Levenberg–Marquardt nonlinear least squares fitting algorithm. As manager of the DuPont Applied Statistics Group, he led development of the Product Quality Management methodology and computer systems that implemented the company's continuous improvement initiatives from the mid-1970s to the late 1990s. He won the Shewhart Medal in 1986. He died from a heart attack at the age of 68.