Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many cultures. Corn flour has been important in Mesoamerican cuisine since ancient times and remains a staple in the Americas. Rye flour is a constituent of bread in central and northern Europe.

Cereal flour consists either of the endosperm, germ, and bran together (whole-grain flour) or of the endosperm alone (refined flour). Meal is either differentiable from flour as having slightly coarser particle size (degree of comminution) or is synonymous with flour; the word is used both ways. For example, the word cornmeal often connotes a grittier texture whereas corn flour connotes fine powder, although there is no codified dividing line.

The CDC has cautioned not to eat raw flour doughs or batters. Raw flour can contain bacteria like E. coli and needs to be cooked like other foods.