The Zastava M21 assault rifle was developed and is manufactured by the Serbian Zastava Arms company. This weapon is produced since 2004. It is based on the Kalashnikov AK-74 design, but has a number of improvements. The Zastava M21 is currently in service with Serbia, and replaces the previous M70, M72 and M92 7.62 mm assault rifles, that are license-produced versions of the AK-47 and its derivatives. Other operators of the M21 are Bosnia and Herzegovina, Cameroon, Jordan, Macedonia and Peru.

This assault rifle is chambered for a standard NATO 5.56�45 mm ammunition. It is a gas-operated, magazine fed, selective fire weapon. The M21 has fire mode selectors on either side of the receiver. Both of them have �safe�, �semi-auto� and �full-auto� settings. The Kalashnikov-type fire mode selector is located on the right side, while another is located on the left side and is operated by the thumb. Such selector design was influenced by Galil assault rifle, produced in Israel.

The Zastava M21 has a folding stock, which folds to the right side. When folded it do not obstructs the fire mode selector and trigger. Both polymer and metal stocks are available.

This weapon is fed from 30-round capacity magazines.

The Zastava M21 has conventional iron sights, with two settings for 300 and 500 meters. A special attachment with Picatinny-type rail for optical scopes and night sights can be fitted.

Assault rifle is compatible with BGP 40 mm under barrel grenade launcher. Alternatively it can be fitted with a knife-bayonet.