Robert Samuel Langer, Jr(born August 29, 1948) is an American engineer, scientist, entrepreneur, inventor and the David H. Koch Institute Professor 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 Division of Health Sciences and Technology and the David H. Koch Institute for Integrative Cancer Research. 

He is a widely recognized and cited researcher in biotechnology, especially in the fields of drug delivery systems and tissue engineering. He has been cited over 169,000 times and has an h-index of 210 as of April 3, 2015.He received the Perkin Medal, recognized as the highest honor given for outstanding work in applied chemistry in the United States in 2012.