Robert Samuel Langer Jr. FREng (born August 29, 1948) is an American chemical engineer, scientist, entrepreneur, inventor and one of the twelve Institute Professors at the Massachusetts Institute of Technology. He was formerly the Germeshausen Professor of Chemical and Biomedical Engineering and maintains activity in the Department of Chemical Engineering and the Department of Biological Engineering at MIT. He is also a faculty member of the Harvard–MIT Program in Health Sciences and Technology and the Koch Institute for Integrative Cancer Research.