Brazil nut, (Bertholletia excelsa), also called Pará nut, edible seed of a large South American tree (family Lecythidaceae) found in the Amazonian forests of Brazil, Peru, Colombia, and Ecuador. The Brazil nut is particularly well known in the Brazilian state of Pará, where it is called castanha-do-pará (Pará nut) and is grown as one of the major commercially traded nuts in the world. Brazil nuts are commonly eaten raw or blanched and are high in protein, dietary fibre, thiamin, selenium, copper, and magnesium. The oil is often used in shampoos, soaps, hair conditioners, and skin-care products.

Brazil nut Hard, indehiscent fruits of the Brazil nut tree (Bertholletia excelsa). The fruit on the left has been opened to reveal the large edible seeds in their shells. The tree is found in the Amazonian forests of Brazil, Peru, Colombia, and Ecuador. Fernanda Preto/Alamy

The Brazil nut tree grows wild in stands in the Amazon River basin. It will often tower over its neighbours, reaching heights of 49 metres (160 feet) or more, with its crown spreading over 30 metres (100 feet) in diameter. The buttressed trunk is usually less than 2 metres (6.6 feet) across, but 3-metre (10-foot) specimens have been observed. The trees bear ovate leaves with smooth margins and produce unusual, white to cream-coloured flowers with bilateral symmetry.

The hard-walled fruits are spherical pods, 8–18 cm (3–7 inches) in diameter, that resemble large coconuts hanging at the ends of the tree’s thick branches. A typical 15-cm (6-inch) pod can weigh up to 2.3 kg (5 pounds) and contains 12–24 nuts, or seeds, that are arranged like the sections of an orange. A mature tree will produce more than 300 pods, which ripen and fall to the ground from January to June. The pods are harvested from the forest floor, and the seeds are taken out, dried in the sun, and then washed and exported while still in their shells. The brown shell is very hard and has three sides.

Brazil nuts are some of the most valuable non-timber products in the Amazon but are extremely sensitive to deforestation, because of their complex ecological requirements. The trees produce fruit only in undisturbed habitats and cannot be cultivated in pure stands. They require large native bees for the pollination of their semi-enclosed flowers and rely solely on agoutis (medium-sized rodents) for the dispersal of their seeds. Brazil nuts are primarily harvested in the wild by local people. Many forest-based communities depend on the collection and sale of Brazil nuts as a vital and sustainable source of income, and the sweet nuts provide protein and calories for tribal, rural, and even urban Brazilians. Native Amazonians use the empty pods as containers and brew the bark to treat liver ailments.

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Brazil nuts are related to a number of other tropical trees valued for their fruits and nuts, including the cannonball tree (Couroupita guianensis), the anchovy pear (Grias cauliflora), and the monkey pot (Lecythis species).