A musket is a muzzle-loaded long gun that appeared as a smoothbore weapon in the early 16th century, at first as a heavier variant of the arquebus, capable of penetrating plate armour. By the mid-16th century, this type of musket gradually disappeared as the use of heavy armour declined, but musket continued as the generic term for smoothbore long guns until the mid-19th century. In turn, this style of musket was retired in the 19th century when rifled muskets using the Minié ball became common. The development of breech-loading firearms using self-contained cartridges and the first reliable repeating rifles produced by Winchester Repeating Arms Company in 1860 also led to their demise. By the time that repeating rifles became common, they were known as simply "rifles", ending the era of the musket.

A muzzleloader is any firearm in which the user loads the projectile and the propellant charge into the muzzle end of the gun. This is distinct from the modern designs of breech-loading firearms, in which user loads the ammunition into the breech end of the barrel. The term "muzzleloader" applies to both rifled and smoothbore type muzzleloaders, and may also refer to the marksman who specializes in the shooting of such firearms. The firing methods, paraphernalia and mechanism further divide both categories as do caliber.