soybean, soya bean, or soy pea, leguminous plant (Glycine max, G. soja, or Soja max) of the family Leguminosae (pulse family), native to tropical and warm temperate regions of Asia, where it has been cultivated as a principal crop for at least 5,000 years. There are over 2,500 varieties in cultivation, producing beans of many sizes, shapes, and colors. As a crop, soybeans are high in yield and easy to harvest; they grow well wherever corn is cultivated.

In East Asia, soybeans are used in a multitude of forms, e.g., as soy sauce, soybean meal, vegetable oil, tofu (bean curd), miso (fermented soybean paste), and soy milk, and as a coffee substitute. In the United States, soybean products such as tofu, miso, and soy milk have become especially popular in lowfat and vegetarian diets (see vegetarianism). The green crop is used for forage and hay, and the cake as stock feed and as fertilizer. Soybean oil is used commercially in the manufacture of glycerin, paints, soaps, rubber substitutes, plastics, printing ink, and other products.

Cultivation of the soybean, long confined chiefly to China, gradually spread to other countries. During World War II soybeans became important in both North America and Europe chiefly as substitutes for other protein foods and as a source of edible oil. In the United States they are now a leading crop, and Brazil, Argentina, and Paraguay also are significant soybean-exporting nations. China and Japan are by far the largest importers of soybeans.

Soybeans are classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Leguminosae.

Annual legume (Glycine max, or G. soja) of the pea family (see legume) and its edible seed. The soybean plant has an erect, branching stem, white to purple flowers, and one to four seeds per pod. It was probably derived from a wild plant of East Asia, where it has been cultivated for some 5,000 years. Introduced into the U.S. in 1804, it began to be farmed widely as a livestock feed in the 1930s, and the U.S. is now the world's foremost soybean producer. Economically the world's most important bean, the soybean provides vegetable protein for millions of people and ingredients for hundreds of chemical products, including paints, adhesives, fertilizers, insect sprays, and fire-extinguisher fluids. Because soybeans contain no starch, they are a good source of protein for diabetics. Processed for food, soybean oil is made into margarine, shortening, and vegetarian cheeses and meats. Soybean meal serves as a high-protein meat substitute in many food products, including baby foods. Other food products include soybean milk, tofu, salad sprouts, and soy sauce.

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