Irving Lerner "Irv" Weissman (born Great Falls, Montana, October 21, 1939) is a Professor of Pathology and Developmental Biology at Stanford University where he is the Director of the Stanford Institute of Stem Cell Biology and Regenerative Medicine along with Michael Longaker. Weissman was raised in Great Falls, Montana and started his scientific career at the there. He obtained his MD from Stanford University in 1965 after earning a BS from Montana State University in 1961. His research has since focused on hematopoietic stem cell biology.