In firearm designs, the term single-shot refers to guns that can hold only a single round of ammunition inside and thus must be reloaded manually after every shot. Compared to multi-shot repeating firearms ("repeaters"), single-shot designs have no moving parts other than the trigger, hammer/firing pin or frizzen, and therefore do not need a sizable receiver behind the barrel to accommodate a moving action, making them far less complex and more robust than revolvers or magazine/belt-fed firearms, but also with much slower rates of fire.
The history of firearms began with muzzleloading single-shot firearms such as the hand cannon and arquebus, then multi-barreled designs such as the derringer appeared, and eventually many centuries passed before breechloading repeating firearms became commonplace. Although largely disappeared from military usage due to insufficient firepower, single-shot firearms are still produced by many manufacturers in both muzzleloading and cartridge-firing varieties, from zip guns and ultra-concealable pocket pistols to the highest-quality hunting and match rifles.