The M109, an American-designed self-propelled howitzer, replaced the M44 in the US army in 1961. Italy received M44s post-war as US aid, however with further negotiations Italy later acquired M109s, upgrading some to the M109L standard with OTO Melara 155 mm cannons and adding rammer devices. While not heavily armoured, the M109 could withstand small arms fire and some shell splinters. It reached speeds of 35 km/h and had a range of 216 miles. The Italian army used M109s in peacekeeping operations but phased them out in the early 2000s for the PzH 2000 artillery piece. Leonardo also created an upgrade for the M109 with a longer-range cannon and Italian Vulcano guided munitions.

It was introduced in Update "Kings of Battle". The M109G (Italy) has little to no armour, being able to be penetrated from low calibre autocannon fire, including 14.5 mm HMGs. This does not mean that the M109 is bad; with a powerful 155 mm cannon, its HE shells are enough to overpressure or even penetrate the armour of most tanks. The tank does have a very long reload rate and a poor turret traverse speed, it is recommended using the M109 for ambushes, flanking with allies, launching a HE shell at a weakspot and then retreat to safety to reload. Against heavy tanks, it is recommended to aim for the top of the turret or below the chassis if possible.