A cap gun, cap pistol, or cap rifle is a toy gun that creates a loud sound simulating a gunshot and smoke when a small percussion cap is ignited. Cap guns were originally made of cast iron, but after World War II were made of zinc alloy, and most newer models are made of plastic. Cap guns get their name from the small discs of shock-sensitive explosive compounds that provide the noise and smoke, effectively the same as the Maynard tape primer and percussion caps used in real firearms of the mid to late 1800s but usually smaller and made from cheap plastic or paper. Some are arranged in plastic rings of eight or twelve. There are also single caps, roll caps, disk caps, and cap strips all of which are actually extremely small versions of percussion fireworks. Armstrong's mixture is often used today as the explosive, but previously the tiny powder charge was a simple mixture of potassium perchlorate, sulfur, and antimony sulfide sandwiched between two paper layers that hold in the gases long enough to give a sound report when the cap is struck.

Toy guns are toys which imitate real guns, but are designed for recreational sport or casual play by children. From hand-carved wooden replicas to factory-produced pop guns and cap guns, toy guns come in all sizes, prices and materials such as wood, metal, plastic or any combination thereof. Many newer toy guns are brightly colored and oddly shaped to prevent them from being mistaken for real firearms.