Neal D. Barnard is an American physician, author, clinical researcher, and founding president of the Physicians Committee for Responsible Medicine (PCRM), an international network of physicians, scientists, and laypeople who promote preventive medicine, conduct clinical research, and promote higher standards in research.

An advocate of low-fat vegan diets, he has also conducted research into alternatives to animal experimentation and has been active in the animal rights movement. As of 2011, he is an adjunct associate professor of medicine at the George Washington University School of Medicine and Health Sciences, serves as president of The Cancer Project, and heads the Washington Center for Clinical Research, a PCRM subsidiary..