A chainsaw (or chain saw) is a portable, mechanical saw powered by a gasoline two-stroke engine.

It is used in activities such as tree felling, limbing, bucking, pruning, by tree surgeons to fell trees and remove branches and foliage, to fell snags and assist in cutting firebreaks in wildland fire suppression, and to harvest firewood. 

Chainsaws with specially designed bar and chain combinations have been developed as tools for use in chainsaw art and chainsaw mills.