A series of Serbian 5.56×45mm NATO assault rifles. Heavily based on the AK platform, it was designed by Marinko Petrović and manufactured by Zastava Arms since 2004.

The current models use a 1.5mm thick stamped receiver. The M21 can incorporate picatinny rails for mounting accessories like optical sights, foregrips, bipods, etc.

The Zastava M21 is gas operated, long stroke piston with a rotating bolt locking system rifle. It features a hard chromium-plated, cold forged standard rifled or an optional polygonal rifled barrel, integrated 22mm muzzle device grenade launcher, heavy-duty dark/black synthetic furniture similarly to the AK-74M with a polymer side-folding stock, and side optics rail as standard (optional adapter base for cover mounted picatinny rail also available). The rifle can also mount a 40mm underbarrel grenade launcher. It is fed with standard 30-round magazine. The cyclic rate of fire is 680 rounds per minute, sustained one is 120 RPM.

Variants

• M21 A – Standard baseline assault rifle.
• M21 ABS – Built-in picatinny rail system.
• M21 S – Compact short barrel assault rifle.
• M21 SBS – Built-in picatinny rail system.
• M21 C – Carbine.
• M21 BS – Built-in picatinny rail system.