Chestnuts should not be confused with horse chestnuts (genus Aesculus), which are not related to Castanea and are named for producing nuts of similar appearance, but which are mildly poisonous to humans, nor should they be confused with water chestnut (family Cyperaceae), which are also unrelated to Castanea and are tubers of similar taste from an aquatic herbaceous plant.
Other trees commonly mistaken for chestnut trees are the chestnut oak (Quercus prinus) and the American beech (Fagus grandifolia), both of which are also in Fagaceae.