Malcolm Robert Irwin (2 March 1897, Artesian, South Dakota – 12 October 1987, Madison, Wisconsin) was an American agronomist and pioneering immunogeneticist.
Irvin then began graduate study under Ernest W. Lindström (1891–1948) at the recently established department of genetics of Iowa State University and received his Ph.D. there in 1928.
At the Rockefeller Institute he was influenced by the immunohematologist Karl Landsteiner and by the immunochemists Oswald Avery and Michael Heidelberger.
From 1951 to 1965 he was also the chair of the genetics department, building powerful expertise in immunogenetics and founding a "school" of blood group scientists.
Irwin also investigated the immunological processes after tissue transplantation, as well as cellular antibody production.