This article addresses small-arms cartridges. For cartridges used with larger arms, see Artillery#Ammunition and Shell (projectile).

A cartridge (also called a round or a shell) is a type of ammunition packaging a bullet or shot, a propellant substance (usually either smokeless powder or black powder) and a primer within a metallic, paper, or plastic case that is precisely made to fit within the firing chamber of a firearm. The primer is a small charge of an impact-sensitive or electric-sensitive chemical mixture that can be located at the center of the case head (centerfire ammunition), inside a rim (rimfire ammunition), or in a projection such as in a pinfire or teat-fire cartridge. Military and commercial producers continue to pursue the goal of caseless ammunition. A cartridge without a bullet is called a blank. One that is completely inert (contains no active primer and no propellant) is called a dummy.