Robert Joseph Lefkowitz (born April 15, 1943) is an American physician (internist and cardiologist) and biochemist. He is best known for his groundbreaking discoveries that reveal the inner workings of an important family G protein-coupled receptors, for which he was awarded the 2012 Nobel Prize for Chemistry with Brian Kobilka. He is currently an Investigator with the Howard Hughes Medical Institute as well as a James B. Duke Professor of Medicine and Professor of Biochemistry and Chemistry at Duke University.