Conkers is a traditional children's game in Great Britain and Ireland played using the seeds of horse chestnut trees—the name 'conker' is also applied to the seed and to the tree itself. The game is played by two players, each with a conker threaded onto a piece of string: they take turns striking each other's conker until one breaks.

The genus Aesculus, with species called buckeye and horse chestnut, comprises 13–19 species of flowering plants in the family Sapindaceae. They are trees and shrubs native to the temperate Northern Hemisphere, with six species native to North America and seven to 13 species native to Eurasia. Several hybrids occur. Aesculus exhibits a classical Arcto-Tertiary distribution.