Walter Willett, M.D., Dr.P.H. (born in 1945 in Hart, Michigan) is an American physician and nutrition researcher. Currently, Willett is the Fredrick John Stare Professor of Epidemiology and Nutrition and the chair of the department of nutrition at Harvard School of Public Health. He is also a professor of medicine at Harvard Medical School.
Willett is the principal investigator of the second Nurses' Health Study, a compilation of studies regarding the health of older women and their risk factors for major chronic diseases. He has published more than 1,000 scientific articles regarding various aspects of diet and disease  and is the second most cited author in clinical medicine.
In Willett is perhaps best known for his 2001 book Eat, Drink, and Be Healthy, which presents nutritional information and recommendations based on what was then the consensus of nutrition scientists. His book is critical of many popular misconceptions about diet and nutrition, including ideas presented by guidelines from American organizations such as the USDA. Willett is frequently quoted by the media in articles regarding nutrition.
- B.S. 1966, Michigan State University
- M.D. 1970, University of Michigan Medical School
- M.P.H. 1973, Harvard School of Public Health
- Dr.P.H. 1980, Harvard School of Public Health, Epidemiology
- Chair, 1991, Department of Nutrition, Harvard School of Public Health 
Influence on Harvard meal plans and cafeterias
Willett has been actively involved in helping Harvard University food services to update their offerings along current nutritional guidelines. While his work has influenced the menu choices, students and Willett have noted that the menus still have a long way to go to reflect the currently available nutrition science.
- Nutritional Epidemiology 1998 ISBN 0-19-512297-6
- Eat, Drink, and be Healthy: The Harvard Medical School Guide To Healthy Eating 2005 ISBN 0-684-86337-5
- Eat, Drink, and Weigh Less 2007 ISBN 1-4013-0892-9
- The Fertility Diet 2008 ISBN 0-07-149479-0
- More than 1,000 scientific articles 
- "Honda Worldwide | September 29, 2004 "Honda Prize Awarded to Dr. Walter C. Willet"". World.honda.com. Retrieved 2011-06-08.
- Burros, Marian. "EATING WELL; At a Harvard Cafe, Health for Lunch". The New York Times. Retrieved 27 February 2016.
- "Walter Willet". Harvard University. Harvard University. Retrieved 27 February 2016.
- "Walter C. Willett, MD, Dr.PH". BCRF: Breast Cancer Research Foundation. Retrieved 27 February 2016.
- "The Nurses' Health Study". Harvard University. Harvard University. Retrieved 27 February 2016.
- "NCBI search". Ncbi.nlm.nih.gov. 2011-03-18. Retrieved 2011-06-08.
- "First Bimonthly Period of 2007 - Top 10 Researchers In Clinical Medicine". in-cites. Retrieved 2011-06-08.
- HPH NOW, August 24, 2001, Nutrition Book Author Willett Rebuilds USDA Food Pyramid Archived September 3, 2006, at the Wayback Machine.
- A reversal on carbs, Marni Jameson, Los Angeles Times, December 20, 2010.
- Taking Diet Soda Study with a Grain of Salt, ABC News, February 8, 2011.
- Interview: Walter Willett, M.D., PBS Frontline, April 8, 2004.
- The truth on foods and fats, Amanda Spake, U.S. News & World Report, July 4, 2004.
- At Harvard, Whole-Grain Concerns, Candy Sagon, Washington Post, March 8, 2006.
- Transcript - The search for Optimal Diets: A Progress Report presented at the Honda Foundation
- Information on Eat, Drink, and be Healthy