Seitan (UK: /ˈseɪtæn/, US: /-tɑːn/; Japanese: セイタン) is a food made from gluten, the main protein of wheat. It is also known as miànjīn (Chinese: 麵筋), fu (Japanese: 麩), milgogi (Korean: 밀고기), mì căn, wheat meat, gluten meat, or simply gluten.

Wheat gluten is an alternative to soybean-based foods, such as tofu, which are sometimes used as a meat alternative. Some types of wheat gluten have a chewy or stringy texture that resembles meat more than other substitutes. Wheat gluten is often used instead of meat in Asian, vegetarian, vegan, Buddhist, and macrobiotic cuisines. Mock duck is a common use.

Wheat gluten first appeared during the 6th century as an ingredient for Chinese noodles. It has historically been popular in the cuisines of China, Japan and other East and Southeast Asian nations. In Asia, it is commonly found on the menus of restaurants catering primarily to Buddhist customers who do not eat meat.

Gluten is traditionally extracted from wheat flour. A dough is washed in water until most of the starch granules have been removed, leaving behind the sticky, insoluble gluten as an elastic mass. This mass is cooked in a variety of ways and eaten. There are several industrial methods for separating gluten from starch.

Powdered forms of wheat gluten are also industrially produced and sold as an alternative way to make seitan. Their production involves hydrating hard wheat flour to activate the gluten, and then processing the hydrated mass to remove the starch. This leaves only the gluten, which is then dried and ground back into a powder, and can be used by consumers to make a seitan-like product.

When prepared to eat, seitan is generally marinated with a variety of ingredients.

Called miànjīn (麵筋) meaning wheat tendon, this way of preparing wheat gluten has been documented in China since the 6th century. It is widely consumed by the Chinese as a substitute for meat, especially among monastic and lay adherents of Chinese Buddhism. The oldest reference to wheat gluten appears in the Qimin Yaoshu, a Chinese agricultural encyclopedia written by Jia Sixie in 535. The encyclopedia mentions noodles prepared from wheat gluten called bótuō (餺飥). Wheat gluten was known as miànjīn (麵筋) by the Song dynasty (960–1279).

Traditionally food is perceived as kitchen medicine within Chinese culture, gluten is part of traditional Chinese food therapy called shí liáo (食療), and was prescribed by traditional Chinese medicinal physicians to treat a wide range of illnesses and disease.