The tanks' main armament is a smooth-bore or rifled gun (most of modern tanks are fitted with smooth-bore guns). The guns are used for direct fire, although indirect fire is also possible. The latest tanks are armed either with 120 mm gun (NATO calibre) or 125 mm gun (originated in the former Soviet Union). советский калибр»). The gun barrels are usually fitted with a thermal sleeve.

The tank guns can fire various types of ammunition intended for destruction both armoured and unarmoured targets: armour-piercing fin-stabilised discarding sabot (APFSDS), high-explosive squash-head (HESH), also called high-explosive plastic (HEP), high-explosive anti-tank (HEAT), high-explosive fragmentation (HE-FRAG), smoke, canister, etc. The main anti-tank ammunition types are APFSDS and HEAT (the former penetrates the armour by means of a long-rod penetrator made either of special steel or tungsten allow or depleted uranium, while the other, by using a high energy jet of melted copper allow).

The smooth-bore guns can also fire laser beam-riding anti-tank guided missiles which can destroy targets at distances of up to 5 km (while APFSDS and HEAT rounds are only effective within distances of up to 3 km).

The modern tanks are armed with at least two machine guns, one of which is mounted coaxially with the main gun, while the other is installed on the turret roof and is used for firing at both ground and air targets.