thumb|[[Aesculus glabra Ohio buckeye ]]

thumb|Flower of [[Aesculus x carnea|Aesculus × carnea, the red horse-chestnut]]

thumb|Germinating seed of a horse-chestnut still half-enclosed in its shell, while the root has already reached the soil

The genus Aesculus () is a genus of flowering plants in the family Sapindaceae. They are trees and shrubs, mostly native to the temperate Northern Hemisphere, but one species (A. assamica) into subtropical areas of southeast Asia. The Plants of the World Online (POWO) database currently accepts 12 species, with seven species native to North America, four native to Asia, and one native to Europe; some other authors have accepted more species. Hardin (1957–1960) accepted 13 species, and Harris et al. (2009) accepted 16 species. Six natural hybrids occur,

thumb|250px| Half-open leaf bud of a horse chestnut Aesculus hippocastanum.

Carl Linnaeus named the genus Aesculus after the Roman name for an edible acorn. The genus was considered to be in the ditypic family Hippocastanaceae along with Billia,

In Geneva, Switzerland, an official chestnut tree is used to indicate the beginning of the Spring; every year since 1818, the tree is observed by the secretary of the Grand Council of Geneva (the local parliament), and the opening of the first leaf is recorded and announced publicly. Over the years, four different horse chestnut trees have been used for these recordings.

In the 1840 U.S. presidential campaign, candidate William Henry Harrison called himself the "log cabin and hard cider candidate", portraying himself sitting in a log cabin made of buckeye logs and drinking hard cider, causing Ohio to become known as "the Buckeye State".

  • Germplasm Resources Information Network: Aesculus
  • Forest, F., Drouin, J. N., Charest, R., Brouillet, L., & Bruneau A. (2001). "A morphological phylogenetic analysis of Aesculus L. and Billia Peyr. (Sapindaceae)". Can. J. Bot. 79 (2): 154–169. .
  • Aesculus glabra (Ohio buckeye) King's American Dispensatory
  • Winter ID pictures