Chestnut, a nut-bearing hardwood tree related to the oak and beech. Its burlike fruit contains one to three nuts, also called chestnuts, that resemble large acorns flattened on one side. After a heavy frost, the rough, prickly burs open and the nuts fall to the ground. Chestnuts can be eaten roasted or they can be boiled and used in poultry stuffing. Chestnut timber, like oak, is hard and durable. It is used in building construction, paneling, and the manufacture of furniture. The bark is a source of tannin.

The American chestnut grows 100 feet (30 m) tall and has white, heavily scented flowers that bloom in early summer. Each bur holds two to three nuts. Dwarf chestnuts, or chinquapins, averaging 40 feet (12 m) in height, bear a single nut in each bur. Two species of chinquapins noted for their sweet, edible nuts are the Allegheny chinquapin, of the eastern United States, and the Florida, or trailing, chinquapin, of the southern United States.

The European chestnut, Chinese chestnut, and Japanese chestnut have larger nuts than the American. They are cultivated for their nuts and as ornamentals.

Virtually all American chestnuts have been destroyed by chestnut blight, a fungus disease introduced into the United States from Asia in the early 1900's. Sprouts sometimes grow from roots or old stumps, but are eventually killed by the fungus. Attempts are being made to prevent these sprouts from dying, and to develop hybrids combining the disease resistance of Asian species with the American chestnut's ability to grow in a wide range of soils and climates.

Chestnuts and chinquapins belong to the beech family, Fagaceae. The American chestnut is Castanea dentata; the European, C. sativa; the Chinese, C. mollissima; the Japanese, C. crenata. The Allegheny chinquapin is C. pumila; the Florida, C. alnifolia. Chestnut blight is caused by the fungus Endothia parasitica.