A sniper is an infantry soldier who specializes in shooting from a concealed position over longer ranges than regular infantry, often with a specially designed or adapted sniper rifle. It requires skill in marksmanship, camouflage and field craft.

The term sniper is attested from 1824 in the sense of “sharpshooter.” The verb to snipe originated in the 1770s among soldiers in British India-in the sense of: “to shoot from a hidden place,” in allusion to snipe hunting, a game bird known for being extremely difficult to hunt. Those who were skilled at the hunting of this bird were thus dubbed "snipers".

Different countries have different military doctrines regarding snipers in military units, settings, and tactics. Generally, a sniper’s goal in warfare is to reduce the enemy’s fighting ability by striking at a small number of high value targets, such as officers.

Military snipers from the US, UK, and other countries that adopt their military doctrine are typically deployed in two-man sniper teams consisting of a shooter and spotter. The two have different functions and hence their assignment corresponds to their skills, but a common practice is for the shooter and spotter to take turns in order to avoid eye fatigue.

Typical sniper missions include reconnaissance and surveillance, counter-sniper, killing enemy commanders, selecting targets of opportunity, and even anti-matériel tasks (destruction of military equipment), which tend to require use of rifles in the larger calibers such as the .50 BMG. Snipers have of late been increasingly demonstrated as useful by US and UK forces in the recent Iraq campaign in a fire support role to cover the movement of infantry, especially in urban areas.

Since stealth is one of the main issues with being a sniper, many snipers create their own ghillie suits to match the enivroment of their misssion.