The M16A2 is a late Cold War era assault rifle of US origin. It was developed by Fabrique Nationale at the request of the US Marine Corps. The M16A2 is a product improved version of the M16A1. The main improvement is the use of the 5.56x45mm NATO round instead of the older M193 round. When it was introduced in the 1980's the full size M16A2 with iron sights was the main production variant. Nowadays the M4 carbine with the ability to mount optics is considered the main variant.

The M16A2 is a product improved M16A1. The areas of improvement include the round that is fired, the iron sights and a burst fire option instead of full automatic fire. The M16A2 fires a redesigned 5.56x45mm round that uses a faster rifling twist rate. This version of the 5.56x45mm round was also adopted as NATO standard. The M16A2 retains the direct impingement design and rotating bolt. Externally the M16A2 looks very similar to the M16A1 and at a glance only the round forearm identifies the M16A2. A carbine version with shorter barrel and retractable stock was also developed. It was fires named the M16A2 Carbine and was later redesignated as the M4. On the latest models the rear sight and carrying handle have been replaced by a Picatinny rail that allows various optics to be fitted.

The M16A2 fires the 5.56x45mm NATO round from 30 round magazines, although various other capacities are available. The M16A2 is a select fire weapon with a cyclic rate of fire of 700 to 950 rounds per minute. Many rifles in US service feature a three round burst fire selector instead permitting full automatic fire. The effective range is 400 meters, although with optics targets out to 600 m can be engaged.

The first user of the M16A2 was the US marine corps in the mid 1980's, with the US army adopting it in the late 1980's. The M16A2 and its derivatives are widely used around the world and are the standard issue firearm of various nations. The M4 is in use with many special forces units worldwide and many US law enforcement agencies.