A sniper is a military or paramilitary marksman who engages targets from positions of concealment or at distances exceeding the target's detection capabilities. Snipers generally have specialized training and are equipped with telescopic sights. Modern snipers use high-precision rifles and high-magnification optics. They often also serve as scouts or observers feeding tactical information back to their units or command headquarters.
In addition to long-range and high-grade marksmanship, military snipers are trained in a variety of special operation techniques: detection, stalking, target range estimation methods, camouflage, tracking, bushcraft, field craft, infiltration, special reconnaissance and observation, surveillance and target acquisition.
The name sniper comes from the verb to snipe, which originated in the 1770s among soldiers in British India in reference to shooting snipes, a wader that was considered an extremely challenging game bird for hunters due to its alertness, camouflaging color and erratic flight behavior. Snipe hunters therefore needed to be stealthy in addition to being good trackers and marksmen. In the 18th century, letters sent home by English officers in India referred to a day's rough shooting as "going sniping", as it took a skilled flintlock sportsman a lot of patience and endurance to wing-shoot a snipe in flight. Accomplishing such a shot was regarded as exceptional. During the late 18th century, the term snipe shooting was simplified to sniping. This evolved to the agent noun sniper, first appearing by the 1820s. The term sniper became commonplace in the First World War.
The older term sharpshooter comes from the calque of German word Scharfschütze, in use by British newspapers as early as 1801. The word alludes to good marksmanship, itself descendent of the shooting competitions (Schützenfeste) that took place throughout the year in Munich in the 15th century. Small companies of shooters (Schützenfähnlein) from the German states and Swiss cantons would form teams of Scharfschützen for such popular competitions, proudly carrying flags depicting a crossbow on one side and a target musket on the other. The earliest known date for the creation of a shooting club formed specifically for the use of firearms comes from Lucerne, Switzerland, where one club has a charter dating from 1466. During the American Civil War, Confederate marksmen equipped with the imported Whitworth rifles were known as the Whitworth Sharpshooters.
Different countries use different military doctrines regarding snipers in military units, settings, and tactics.
A sniper's primary function in modern warfare is to stay concealed at all times and avoid detection. They provide detailed surveillance from a concealed position, often at long range, and reduce the enemy's combat ability by shooting high-value targets (especially officers and other key personnel). In the process, they cause disruption, pinning down and demoralizing the enemy. Typical sniper missions include managing intelligence information they gather during reconnaissance, target acquisition and impact feedback for air strikes and artillery, assisting employed combat force with accurate fire support and counter-sniper tactics, killing enemy commanders, selecting targets of opportunity, and even destruction of military equipment, which tend to require use of anti-materiel rifles in the larger calibers such as the .50 BMG, like the Barrett M82, McMillan Tac-50, and Denel NTW-20.
Soviet- and Russian-derived military doctrines include squad-level snipers. Snipers have increasingly been 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.
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 a spotter. A common practice is for a shooter and a spotter to take turns to avoid eye fatigue. In most recent combat operations occurring in large densely populated towns, such as Fallujah, Iraq, two teams would be deployed together to increase their security and effectiveness in an urban environment. A sniper team would be armed with a long-range weapon and a rapid-firing shorter-ranged weapon in case of close quarter combat.
The German doctrine of largely independent snipers and emphasis on concealment, developed during the Second World War, has been most influential on modern sniper tactics, and is currently used throughout Western militaries (examples are specialized camouflage clothing, concealment in terrain and emphasis on coup d'œil).
Sniper rifles are classified as crew-served in the United States military. A sniper team (or sniper cell) consists of a combination of at least one primary weapon operator (i.e. the shooter) with other support personnel and force protection elements, such as a spotter or a flanker. Within the Table of Organization and Equipment for both the United States Army and Marine Corps, the shooter does not operate alone, but has a backup shooter trained to fulfill multiple roles in addition to being sniper-qualified in the operation of the main weapon.
The shooter focuses mainly on firing the shot, while the spotter assists in observation of targets, accounts for atmospheric conditions and handles ancillary tasks such as immediate security of their location, communication with other parties (e.g. directing artillery fire and close air support). A flanker is an extra teammate who is tasked to act as a sentry observing areas not immediately visible to the sniper and spotter, assisting with the team's rear security and perimeter defense, and therefore are usually armed with a faster-firing weapon such as an assault rifle, battle rifle or designated marksman rifle. Both the spotter and flanker carry additional ammunition and associated equipment.
The spotter is responsible for detecting, identifying and assigning priority of targets for the shooter, as well as assessing the outcome of the shot. Using a spotting scope and/or a rangefinder, the spotter will predict the external ballistics and read the wind speed using an anemometer or physical indicators like the mirage caused by ground heat. Also, in conjunction with the shooter, the spotter will calculate the distance, shooting angle (slant range), mil-related correction, interference by atmospheric factors and the required leads for moving targets. It is not unusual for the spotter to be equipped with a ballistic table, a notebook or a tablet computer specifically for performing these calculations.
The longest confirmed sniper kill in combat was achieved by an undisclosed member of the Security Service of Ukraine in November 2023, hitting a Russian soldier at a distance of 3,800 m (4,156 yd) during the Russian invasion of Ukraine.
The previous record holder was a member of the Canadian JTF2 special forces who in June 2017 achieved a hit at a distance of 3,540 m (3,871 yd).
In November 2009, Craig Harrison, a Corporal of Horse (CoH) in the Blues and Royals RHG/D of the British Army struck two Taliban machine gunners consecutively south of Musa Qala in Helmand Province in Afghanistan at a range of 2,475 m (2,707 yd) or 1.54 miles using a L115A3 Long Range Rifle.
The QTU Lapua external ballistics software, using continuous doppler drag coefficient (Cd) data provided by Lapua, predicts that such shots traveling 2,475 m (2,707 yd) would likely have struck their targets after nearly 6.0 seconds of flight time, having lost 93% of their kinetic energy, retaining 255 m/s (840 ft/s) of their original 936 m/s (3,070 ft/s) velocity, and having dropped 121.39 m (398 ft 3 in) or 2.8° from the original bore line. Due to the extreme distances and travel time involved, even a light cross-breeze of 2.7 m/s (6.0 mph) would have diverted such shots 9.2 m (360 in) off target, which would have required compensation.
The calculation assumes a flat-fire scenario (a situation where the shooting and target positions are at equal elevation), using British military custom high-pressure .338 Lapua Magnum cartridges, loaded with 16.2 g (250 gr) Lapua LockBase B408 bullets, fired at 936 m/s (3,071 ft/s) muzzle velocity under the following on-site (average) atmospheric conditions: barometric pressure: 1,019 hPa (30.1 inHg) at sea-level equivalent or 899 hPa (26.5 inHg) on-site, humidity: 25.9%, and temperature: 15 °C (59 °F) in the region for November 2009, resulting in an air density ρ = 1.0854 kg/m3 at the 1,043 m (3,422 ft) elevation of Musa Qala. Harrison mentions in reports that the environmental conditions were perfect for long range shooting, "... no wind, mild weather, clear visibility." In a BBC interview, Harrison reported it took about nine shots for him and his spotter to initially range the target successfully.