A bullet-resistant vest (body armor) - is an article of protective clothes that works as a form of armor to minimize injury from projectiles fired from handguns, shotguns and rifles. They are commonly worn by police forces, the military and private security and civilians where legal. However, they are sometimes worn illegally, by those that the relevant government refuses to allow body armor.

The term "bullet-proof" is a misnomer since these vests (depending on their armor level, see below) may provide little or no protection against rifle ammunition or even against handgun ammunition fired from a pistol-caliber carbine. The exception is the common .22LR ammunition, which can usually be stopped by these vests even when fired from a rifle. These vests are usually protective against handgun ammunition fired from handguns (once again, depending on their armor level.)

Vests may be augmented with metal (steel or titanium), ceramic or polyethylene plates that provide extra protection to vital areas. These hard armor plates have proven effective against all handgun bullets and against specific rifles using specific ammunition. Normally referred to as tactical body armor, these types of vests have become standard in military use, as soft body armor only vests are ineffective against most military rifle rounds. The CRISAT NATO standard for body armor specifies the use of titanium backing.

A vest does not protect the wearer by deflecting bullets. Instead, the layers of material catch the bullet and spread its force over a larger portion of the body, absorbing energy more quickly and hopefully bringing it to a stop before it can penetrate into the body. This tends to deform the bullet, further reducing its ability to penetrate.

While a vest can prevent bullet wounds, the wearer still absorbs the bullet's energy, which can cause blunt force trauma. The majority of users experience only bruising, but impacts can cause severe internal injuries. This is considered to be unimportant by many, as it seems guaranteed any bullets or shrapnel with sufficient force to cause notable injuries would do more damage without the vest.

Most vests offer little protection against arrows, ice picks, or stabbing knife blows. As the force is concentrated in a relatively small area with such bladed weapons, the tip of the object can push through the weave of most bullet-resistant fabrics. Specially-designed vests are available that can provide protection against bladed weapons, and sharp objects; they are often used in prison-guard vests.

There are a variety of strategies to achieve stab and slash protection. Some materials like Dyneema do offer considerable protection against these types of threats. This is important for the safety of law enforcement and prison guard personnel.

Bulletproof vests are legal in most countries. One exception is Australia, where body armor has been prohibited for some time. This ban may have its origins in the late 19th century, when the iconic Australian outlaw and folk hero Ned Kelly used home-made armor with mixed results. While the steel armor worn by Kelly defeated the soft lead, low velocity bullets fired by police Martini Henry rifles, it greatly restricted his movement.

United States Law provides that it shall be unlawful for a person to purchase, own, or possess body armor. Many states also have penalties for possession or use of body armor.