The cashew tree (Anacardium occidentale) is a tropical evergreen tree that produces the cashew seed and the cashew apple. The tree can grow as high as 14 m (46 ft), but the dwarf cashew, growing up to 6 m (20 ft), has proven more profitable, with earlier maturity and greater yields. The cashew seed is often considered a nut in the culinary sense; this cashew nut is eaten on its own, used in recipes, or processed into cashew cheese or cashew butter. Like the tree, the nut is often simply called a cashew.

The species is native to Central America, the Caribbean Islands, and northern South America, including northeastern Brazil.Portuguese colonists in Brazil began exporting cashew nuts as early as the 1550s. In 2017, Vietnam, India, and Ivory Coast were the major producers.

The shell of the cashew seed yields derivatives that can be used in many applications including lubricants, waterproofing, paints, and, starting in World War II, arms production. The cashew apple is a light reddish to yellow fruit, whose pulp can be processed into a sweet, astringent fruit drink or distilled into liquor.

The cashew tree is large and evergreen, growing to 14 m (46 ft) tall, with a short, often irregularly shaped trunk. The leaves are spirally arranged, leathery textured, elliptic to obovate, 4–22 cm (1.6–8.7 in) long and 2–15 cm (0.79–5.91 in) broad, with smooth margins. The flowers are produced in a panicle or corymb up to 26 cm (10 in) long; each flower is small, pale green at first, then turning reddish, with five slender, acute petals 7–15 mm (0.28–0.59 in) long. The largest cashew tree in the world covers an area around 7,500 m2 (81,000 sq ft); it is located in Natal, Rio Grande do Norte, Brazil.

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 or red structure about 5–11 cm (2.0–4.3 in) long. It is edible and has a strong "sweet" smell and taste.

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. The true fruit contains a single seed, which is often considered a nut in the culinary sense. The seed is surrounded by a double shell that contains an allergenic phenolic resin, anacardic acid—which is a potent skin irritant chemically related to the better-known and also toxic allergenic oil urushiol, which is found in the related poison ivy. Some people are allergic to cashews, but they are a less frequent allergen than tree nuts or peanuts.

The cashew tree is native to northeast Brazil, but the Portuguese took it to Goa, India, between 1560 and 1565. From there, it spread throughout Southeast Asia, and eventually Africa.