The cashew, Anacardium occidentale, is a tree in the family Anacardiaceae. Its English name derives from the Portuguese name for the fruit of the cashew tree, caju (Portuguese pronunciation), which itself is derived from the indigenous Tupi name, acajú. Originally native to Northeastern Brazil, it is now widely grown in tropical climates for its cashew apples and nuts.

The name Anacardium actually refers to the shape of the fruit, which looks like an inverted heart (ana means "upwards" and -cardium means "heart"). In the Tupian languages acajú means "nut that produces itself".

The cashew tree is large and evergreen, growing to 10-12m (~32 ft) tall, with a short, often irregularly shaped trunk. The leaves are spirally arranged, leathery textured, elliptic to obovate, 4 to 22 cm long and 2 to 15 cm broad, with a smooth margin. The flowers are produced in a panicle or corymb up to 26 cm long, each flower small, pale green at first then turning reddish, with five slender, acute petals 7 to 15 mm long. The largest cashew tree in the world covers an area of about 7,500 square metres (81,000 sq ft).The fruit of the cashew tree is an accessory fruit (sometimes called a pseudocarp or false fruit). What appears to be the fruit is an oval or pear-shaped structure, a hypocarpium, that develops from the pedicel and the receptacle of the cashew flower. Called the cashew apple, better known in Central America as "marañón", it ripens into a yellow and/or red structure about 5–11 cm long. It is edible, and has a strong "sweet" smell and a sweet taste. The pulp of the cashew apple is very juicy, but the skin is fragile, making it unsuitable for transport. In Latin America, a fruit drink is made from the cashew apple pulp which has a very refreshing taste and tropical flavor that can be described as having notes of mango, raw green pepper, and just a little hint of grapefruit-like citrus. The true fruit of the cashew tree is a kidney or boxing-glove shaped drupe that grows at the end of the cashew apple. The drupe develops first on the tree, and then the pedicel expands to become the cashew apple. Within the true fruit is a single seed, the cashew nut. Although a nut in the culinary sense, in the botanical sense the nut of the cashew is a seed. The seed is surrounded by a double shell containing an allergenic phenolic resin, anacardic acid, a potent skin irritant chemically related to the better-known allergenic oil urushiol which is also a toxin found in the related poison ivy.

While native to Northeast Brazil, the Portuguese took the cashew plant to Goa, India, between the years of 1560 and 1565. From there it spread throughout Southeast Asia and eventually Africa.

Nigeria was the world's largest producer of cashew nuts with shell in 2010. Cashew nut production trends have varied over the decades. African countries used to be the major producers before 1980s, India became the largest producer in 1990s, followed by Vietnam which became the largest producer in mid 2000s. Since 2008, Nigeria has become the largest producer. Cashew nuts are produced in tropical countries because the tree is very frost sensitive; they have been adapted to various climatic regions around the world between the latitudes of 25-deg. north and south.