Bonsai is the Japanese art of growing and training miniature trees in pots, developed from the traditional Chinese art form of penjing.

The loanword "bonsai" has become an umbrella term in English, attached to many forms of diminutive potted plants, and also on occasion to other living and non-living things.

Purposes of bonsai are primarily contemplation for the viewer, and the pleasant exercise of effort and ingenuity for the grower. By contrast with other plant cultivation practices, bonsai is not intended for production of food or for medicine. Instead, bonsai practice focuses on long-term cultivation and shaping of one or more small trees growing in a container.

A bonsai is created beginning with a specimen of source material. This may be a cutting, seedling, or small tree of a species suitable for bonsai development. Bonsai can be created from nearly any perennial woody-stemmed tree or shrub species that produces true branches and can be cultivated to remain small through pot confinement with crown and root pruning.