John Yudkin FRSC (8 August 1910 – 12 July 1995) was a British physiologist and nutritionist, and the founding Professor of the Department of Nutrition at Queen Elizabeth College, London.

Yudkin wrote several books recommending low-carbohydrate diets for weight loss, including This Slimming Business (1958). He gained an international reputation for his book Pure, White and Deadly (1972), which warned that the consumption of sugar (sucrose, which consists of fructose and glucose) is dangerous to health, an argument he had made since at least 1957. Specifically, he wrote that sugar consumption was a factor in the development of conditions such as dental caries, obesity, diabetes, and heart attack.