Aesculus hippocastanum is a large deciduous, synoecious tree, commonly known as horse-chestnut or conker tree.

The genus Aesculus ( or ) comprises 13–19 species of trees and shrubs native to the temperate Northern Hemisphere, with 6 species native to North America and 7–13 species native to Eurasia; there are also several hybrids. Aesculus exhibits a classical arcto-Tertiary distribution. The genus has traditionally been treated in the ditypic family Hippocastanaceae along with Billia, but recent phylogenetic analysis of morphological and molecular data has caused this family, along with the Aceraceae (Maples and Dipteronia), to be included in the soapberry family (Sapindaceae).