A gladiator (Latin: gladiator, "swordsman", from gladius, "sword") was an armed combatant who entertained audiences in the Roman Republic and Roman Empire in violent confrontations with other gladiators, wild animals, and condemned criminals. Some gladiators were volunteers who risked their legal and social standing and their lives by appearing in the arena. Most were despised as slaves, schooled under harsh conditions, socially marginalized, and segregated even in death.

Irrespective of their origin, gladiators offered audiences an example of Rome's martial ethics and, in fighting or dying well, they could inspire admiration and popular acclaim. They were celebrated in high and low art, and their value as entertainers was commemorated in precious and commonplace objects throughout the Roman world.

The origin of gladiatorial combat is open to debate. There is evidence of it in funeral rites during the Punic Wars of the 3rd century BCE, and thereafter it rapidly became an essential feature of politics and social life in the Roman world. Its popularity led to its use in ever more lavish and costly spectacles or "gladiatorial games".

The games reached their peak between the 1st century BCE and the 2nd century CE, and they finally declined during the early 5th century after the adoption of Christianity as state religion in the 390s, although "beast hunts" (venationes) were continued into the 6th century.