Hollow point bullets are a type of expanding bullet that has a pit or hollowed out tip. When they hit a target, the hollow tip allows the bullet to deform or expand in a predictable manner, making it look more like a mushroom. This expansion slows the bullet and gives it more stopping power, causing more catastrophic damage to the intended target. Hollow points are preferred by hunters and in self-defense situations because they expand upon impact, causing a more lethal hit without penetrating further than necessary.

Compared to ball ammunition, which is designed with a tough metal covering or jacket over a central core material that is designed to remain intact on impact, hollow-point ammunition penetrates shorter distances in impacted objects, travels through an object less often, cannot penetrate various types of barriers, imparts more energy and damage to an object, ricochets less, and is more effective at rapidly incapacitating a person. However, hollow-point ammunition is significantly more expensive than ball ammunition.

In modern ammunition, the use of hollow points is primarily limited to handgun ammunition, which tends to operate at much lower velocities than rifle ammunition. At rifle velocities, a hollow point is not needed for reliable expansion, and most rifle ammunition makes use of tapered jacket designs to achieve the mushrooming effect. Despite the widespread ban on military use, hollow-point bullets are one of the most common types of bullets used by civilians and police, which is due largely to the reduced risk of hitting unintended targets.