Diet, in relation to food, might mean:
- Diet (nutrition), the sum of the food consumed by an organism or group
- Dieting, the deliberate selection of food to control body weight or nutrient intake
- Diet food, foods that aid in dieting
- Cuisine, the diet of a particular culture
Diet may also mean:
- Diet (assembly), formal deliberative assembly
- The Imperial Diet (German Reichstag): the imperial assembly of the princes of the Holy Roman Empire until 1806
- The Diet of the Empire: (German: Reichstag) legislative assembly of the German Empire 1871–1917
- The Federal Diet: (literally for German: Deutscher Bundestag) federal parliament of Germany
- State Diet: (literally for German: Landtag) state parliament of most of the German federated states
- Diet of Finland: the legislative assembly of the Grand Duchy of Finland from 1809 to 1906
- Diet of Hungary: the legislative assembly of the Kingdom of Hungary from 15th century to 1946
- Diet of Japan: Japan's legislature
- "Diet", an episode of the Adult Swim animated television series, Aqua Teen Hunger Force
- Dietsch (disambiguation): distinguishes the southern dialects in the Middle Dutch language
- DIET: an open-source middleware for high-performance computing, created in 2000 and currently developed by INRIA, École Normale Supérieure de Lyon, CNRS, Claude Bernard University Lyon 1, and the SysFera company.
- Diet, India:'District Institute (or Institutes) of Education and Training' in India