Aesculus hippocastanum is a species of flowering plant in the soapberry and lychee family Sapindaceae. It is a large deciduous, syncecious (hermaphroditic-flowered) tree, commonly known as horse-chestnut or conker tree.

Aesculus hippocastanum is native to a small area in the Pindus Mountains mixed forests and Balkan mixed forests of South East Europe. However, it can be found in many parts of Europe as far north as Gästrikland in Sweden, as well as in many parks and cities in the United States and Canada.