A shotgun shell or shotshell is a self-contained cartridge loaded with lead shot or a shotgun slug which is designed to be fired from a shotgun.
Most shotgun shells are designed to be fired from a smoothbore barrel, but dedicated shotguns with rifled barrels may take a number of different rounds. A rifled barrel will increase the accuracy of slugs, but makes it unsuitable for firing shot, as it imparts a spin to the shot cup, causing a centrifugal force that makes the shot form a hollow "O" shape in flight. Non-lethal shotgun ammunition is available in the form of slugs made of low-density material, such as rubber. See shotgun specialty ammunition for more information.