Grain, any plant of the grass family that is cultivated for its edible grains, or kernels. Botanically, these grains are one-seeded fruits; that is, each grain is a fruit containing only one seed. The term grain is also commonly used for the cereal plant.

Cultivation of grains has been a major element in the development of civilization. They provide humans and other animals with their most important source of plant food. Grains are high in food value, containing considerable amounts of carbohydrates and proteins, as well as vitamins and some fats. The most important grains are wheat, rice, corn, rye, oats, and barley.