Irwin Gillespie Priest (27 January 1886 – 19 July 1932) was an American physicist who specialized in optics. He was president of the Optical Society of America from 1928 to 1929.^[2]

He received his bachelor's degree in 1907 from Ohio University. He went to work for the Bureau of Standards straight from college and after just six years was promoted to Chief of Colorimetry Section of the Optics division. He was named the first honorary lifetime member of the American Oil Chemists' Society in 1913 for his work on oil color grading.^[3]