Ralph Merrill Caldwell

Ralph Merrill Caldwell (June 27, 1903, Brookings, South Dakota – November 2, 1976, College Station, Texas) was an American plant breeder, mycologist, and plant pathologist. Through his work with the U.S. Department of Agriculture and Purdue University, he developed disease-resistant cultivars for a wide variety of plants, including widely-grown wheat cultivars.

Caldwell was a member of the American Phytopathological Society, where he served as President of the North Central Division and Treasurer. He was a fellow of the American Phytopathological Society, the American Society of Agronomy, the Crop Science Society of America, and the American Association for the Advancement of Science. His papers are held by the University of Purdue.