Paintball is a competitive team shooting sport in which players eliminate opponents from play by hitting them with spherical dye-filled gelatin capsules called paintballs that break upon impact. Paintballs are usually shot using low-energy air weapons called paintball markers that are powered by compressed air or carbon dioxide and were originally designed for remotely marking trees and cattle.

The game was invented in Henniker, New Hampshire, June 27, 1981, by Hayes Noel, a Wall Street stock trader, and Charles Gaines, an outdoorsman and writer. A debate arose between the two men about whether a city-dweller had the instinct to survive in the woods against someone who had spent his youth hunting, fishing, and building cabins. A friend of the pair chanced upon an advertisement for Nel-Spot cattle marking guns in a farm catalogue and they were inspired to use them to settle their argument. Shortly after they participated with 10 other men in a capture the flag competition they called the first annual "Survival Game". One hundred acres of forest in New Hampshire were divided in to four quadrants and participants were tasked with collecting a flag from each quadrant and returning to a home base. A forester named G. Ritchie White collected the four flags to win in two hours and fifteen minutes.

The sport is played for recreation and is also played at a formal sporting level with organized competition that involves major tournaments, professional teams, and players. Games can be played on indoor or outdoor fields of varying sizes. A playing field may have natural or artificial terrain which players use for tactical cover. Game types and goals vary, but include capture the flag, elimination, defending or attacking a particular point or area, or capturing objects of interest hidden in the playing area. Depending on the variant played, games can last from minutes to hours, or even days in "scenario play".

The legality of the sport and use of paintball markers varies among countries and regions. In most areas where regulated play is offered, players are required to wear protective masks, use barrel-blocking safety equipment, and strictly enforce safe game rules.

The paintball equipment used may depend on the game type (e.g., woodsball, speedball, scenario), on how much money one is willing to spend on equipment, and on personal preference. However, almost every player will utilize three basic pieces of equipment:

Additional equipment, commonly seen among frequent players, tournament participants, and professional players include:

Paintball is played with a potentially limitless variety of rules and variations, which are specified before the game begins. The most basic game rule is that players must attempt to accomplish a goal without being shot and marked with a paintball. A variety of different rules govern the legality of a hit, ranging from "anything counts" (hits cause elimination whether the paintball broke and left a mark or not) to the most common variation: the paintball must break and leave a mark the size of a US quarter or larger. Eliminated players are expected to leave the field of play; eliminations may also earn the opposing team points. Depending on the agreed upon game rules, the player may return to the field and continue playing, or is eliminated from the game completely.

The particular goal of the game is determined before play begins; examples include capture the flag and elimination. Paintball has spawned popular variants, including woodsball, which is played in the natural environment and spans across a large area. Conversely, the variant of speedball is played on a smaller field and has a very fast pace with games as brief as two minutes fifteen seconds in the (NSL) or lasting up to twenty minutes in the PSP (Paintball Sports Promotions). Another variant is scenario paintball, in which players attempt to recreate historical, or fictional settings.