Hippocastanaceae is the name given to a small group of trees and shrubs, when this group is treated as a familiy. Its most widespread genus is Aesculus (the horse-chestnuts and buckeyes, syn. Pavia). However, the American genus Billia and the Chinese genus Handeliodendron are also sometimes included in this family. A feature of the family is the palmate compound leaves.
Members of this family are closely related to the large, mostly tropical family Sapindaceae, and some systems of plant taxonomy include the members of the Hippocastanaceae, along with members of the Aceraceae, in an enlarged family Sapindaceae. Recent molecular phylogenetic research (Harrington et al. 2005) has shown that while both Aceraceae and Hippocastanaceae are monophyletic in themselves, their removal from Sapindaceae sensu lato would leave Sapindaceae sensu stricto as a paraphyletic group, particularly with reference to the genus Xanthoceras. Therefore it is now usually synonymized with subfamily Hippocastanoideae.