A musket is a muzzle-loaded, smoothbore firearm, fired from the shoulder. Muskets were designed for use by infantry. A soldier armed with a musket had the designation musketman or musketeer.

The musket replaced the arquebus, and was in turn replaced by the rifle (in both cases, after a long period of coexistence). The term "musket" is applied to a variety of weapons, including the long, heavy guns with matchlock, wheel lock or flint lock and loose powder fired with the gun barrel resting on a stand, and also lighter weapons with a snaphance, flintlock, or caplock and bullets using a stabilizing spin (Minié ball), affixed with a bayonet.