A sabot (French: shoe) is a device used in a firearm or cannon to fire a projectile or bullet that is smaller than the bore diameter. Since a strong seal is needed to trap propellant gasses behind the projectile, and keep the projectile centered in the barrel, something is needed to fill the gap between projectile and barrel, which is the role of the sabot. Made of some lightweight material (usually plastic in smallbore guns, and aluminum in cannon), the sabot usually consists of several pieces held in place by the cartridge or a loose connection. When the projectile is fired, the sabot blocks the gas, and accelerates the projectile down the barrel. When the sabot reaches the end of the barrel, the shock of hitting still air pulls the parts of the sabot away from the projectile, allowing the projectile to continue in flight.

Sabots are used to fire the flechettes that form anti-armour kinetic energy penetrators.

For reasons why a smaller diameter projectile is desirable, see external ballistics and terminal ballistics.

Sabot-type shotgun slugs were marketed in the U.S. starting in about 1985. When used with a rifled slug barrel, they offer vastly improved accuracy compared to traditional shotgun slugs. They are now legal for deer hunting in most states.