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:
- * 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 Japan: Japan's legislature