105 mm (4.1 in) is a common NATO-standard artillery and tank gun calibre.
The artillery round is defined by AOP-29 part 3 with reference to STANAG 4425.
Since the early 21st century, most NATO armies have settled on 155 mm (6.1 in) weapons as having a good compromise between range and destructive power whilst having a single calibre, which simplifies logistics; however some military forces have retained 105 mm (4.1 in) towed howitzers for their lighter weight and greater portability, including their rapid airlift and airdrop capabilities.
The lower power and shorter range of 105 mm (4.1 in) ammunition has led to its obsolescence in full-sized self-propelled guns, such as the American M108 howitzer and British FV433 Abbot SPG.
The L7 was widely used by NATO countries, and with it was popularized the now-standard 105×617mmR round, still used both in lighter-weight applications such as the Stingray light tank and the Stryker Mobile Gun System, as well as older MBTs such as the M60 tank.