Duncan G. Steel (born 1951) is an American experimental physicist, researcher and professor in quantum optics in condensed matter physics. He is the Robert J. Hiller Professor of Electrical Engineering, Professor of Physics, Professor of Biophysics, and Research Professor in the Institute of Gerontology at the University of Michigan. Steel is also a Guggenheim Scholar and a Fellow of American Physical Society, the Optical Society of America, and the Institute of Electrical and Electronics Engineers. He coedited the five-volume series on the Encyclopedia of Modern Optics.