The 5.7x28mm round is a pistol cartridge of Belgian origin. It was developed by Fabrique Nationale in the 1980's for use in the P90 sub machine gun. The 5.7x28mm round was the first small caliber high velocity pistol cartridge. The most direct competitor is the 4.6x30mm round developed by Heckler & Koch for the MP7 machine pistol.

The 5.7x28mm is based upon the 5.56x45mm SS109 NATO round, which was also developed by Fabrique Nationale. The case and bullet are reduced in size to create a performance in the 9x19mm range with much improved armor piercing capability. Unlike most pistol cartridges the 5.7x28mm has a long and slim design with bottlenecked case and pointed bullet design. The 5.7mm has only a third of the recoil of the 5.56mm NATO and two-thirds of the 9x19mm. The 5.7x28mm allows for a higher magazine capacity than other alternatives for the 9mm, such as the .40 S&W and .357 SIG rounds.

The 5.7x28mm round was designed for the P90 sub machine gun. The P90 has a unique design since it uses a 50 round translucent magazine that lies on top of the weapon. The Fiveseven pistol with conventional 20 round magazine also uses the 5.7x28mm round.

The 5.7x28mm round provides nearly the same lethality as the 9x19mm round. It is very good at piercing armor since it is able to pierce 1.6mm titanium plus 20 layers of kevlar out to 150 meters, which corresponds to most combat body armor and helmets. The maximum effective range is 200 meters for both the FMJ and JHP rounds. The SB193 has a much reduced range of 50 to 100 meters and the V-max bullets can be used out to 150 meters.

The 5.7x28mm round is mainly used by law enforcement units around the world, but mainly in Europe and the USA. The P90 is also in use with special units in the military. In some nations 5.7mm weapons are available to the public with not all types of ammunition being freely available.