The Battle of the Catalaunian Plains, also called the Battle of the Campus Mauriacus, Battle of Châlons, Battle of Troyes or the Battle of Maurica, took place on June 20, 451 AD, between a coalition, led by the Roman general Flavius Aetius and the Visigothic king Theodoric I, against the Huns and their vassals, commanded by their king, Attila. It proved one of the last major military operations of the Western Roman Empire, although Germanic foederati composed the majority of the coalition army. Whether the battle was of strategic significance is disputed; historians generally agree that the siege of Aurelianum was the decisive moment in the campaign and stopped the Huns' attempt to advance any further into Roman territory or establish vassals in Roman Gaul. However, the Huns successfully looted and pillaged much of Gaul and crippled the military capacity of the Romans and Visigoths. Attila died only two years later, in 453; after the Battle of Nedao in 454 AD, the coalition of the Huns and the incorporated Germanic vassals gradually disintegrated.

Attila, frequently called Attila the Hun, was the ruler of the Huns from 434 until his death, in March 453. He was also the leader of an empire consisting of Huns, Ostrogoths, Alans, and Bulgars, among others, in Central and Eastern Europe.