Seitan is a food made from gluten, the main protein of wheat. It is also known as miànjīn, fu, milgogi, wheat meat, gluten meat, or simply gluten. It is made from vital wheat gluten, a flour-like substance primarily consisting of gluten extracted from wheat flour.

Gluten is a structural protein naturally found in certain cereal grains. The term gluten usually refers to a wheat grain's prolamins, specifically glutelin proteins, that naturally occur in many cereal grains, and which can trigger celiac disease in some people. The types of grains that contain gluten include all species of wheat, and barley, rye, and some cultivars of oat; moreover, cross hybrids of any of these cereal grains also contain gluten, e.g. triticale. Gluten makes up 75–85% of the total protein in bread wheat.