Abstract: A saw chain sharpener for a chain saw and a chain saw having a sharpener in which the bottom surfaces of the cutting teeth of a conventional bottom sharpened saw chain are conveniently sharpened automatically by running the chain under power through the sharpener. The saw chain can be sharpened using the sharpener in a matter of typically twenty to thirty seconds without removing the chain from the chain bar. The sharpener is preferably adapted to be removably mounted to a bracket which is itself preferably removably disposed on the chain saw. The sharpener comprises a sharpening tooth disposed in a housing which is mounted on the chain bar. A top surface of the sharpening tooth frictionally engages bottom surfaces of the cutting teeth of the chain as the chain is run under power. A device for dispensing a sharpening compound to the sharpening tooth during sharpening may be disposed on the sharpener housing.