A Rifled Muzzle Loader (RML) is a type of large artillery piece invented in the mid 18th century. In contrast to smooth bore cannon which preceded it, the rifling of the gun barrel allowed much greater accuracy and penetration as the spin induced to the shell gave it directional stability. Typical guns weighed 30 tonnes with 10" diameter muzzles, and were installed in forts and ships.

This new gun (and the Rifled Breech Loader (RBL) which followed it) generated a huge arms race in the late 18th century, with rapid advances in fortifications and ironclad warships.