Hippocastanoideae is a subfamily of flowering plants in the soapberry family Sapindaceae.

[1] The group was formerly treated as the separate families Aceraceae and Hippocastanaceae.

Molecular phylogenetic research by Harrington et al. (2005)[2] has shown that while both the Aceraceae and Hippocastanaceae are monophyletic in themselves, their removal from the Sapindaceae sensu lato would leave Sapindaceae sensu stricto as a paraphyletic group, particularly with reference to the genus Xanthoceras.

The most widespread genera are Acer (the maples) and Aesculus (the horse chestnuts and buckeyes).

[3] Acer Linnaeus Maples 160 Aesculus Linnaeus Horse-chestnuts & buckeyes 13-19 Billia Peyeitsch 2 Dipteronia Oliver 2 Handeliodendron Rehder 1 Media related to Hippocastanoideae at Wikimedia Commons