A musketeer was a type of soldier equipped with a musket. Musketeers were an important part of early modern warfare, particularly in Europe, as they normally comprised the majority of their infantry. The musketeer was a precursor to the rifleman. Muskets were replaced by breech loading rifles as the almost universal firearm for modern armies during the period 1850 to 1870. The traditional designation of "musketeer" for an infantry private survived in the Imperial German Army until World War I.

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.