Aurelian (Latin: Lucius Domitius Aurelianus; 9 September 214 – c. October 275) was a Roman emperor, who reigned during the Third Century Crisis, from 270 to 275. As emperor, he won an unprecedented series of military victories which reunited the Roman Empire after it had nearly disintegrated under the pressure of barbarian invasions and internal revolts.

Born in humble circumstances, near the Danube River, he entered the Roman military in 235, and climbed up the ranks. He would go on to lead the cavalry of the emperor Gallienus, until Gallienus' assassination in 268. Following this, Claudius Gothicus became emperor, until his own death in 270. Claudius' brother, Quintillus ruled the empire for three months, before Aurelian became emperor.

During his reign, he defeated the Alamanni after a devastating war. He also defeated the Goths, Vandals, Juthungi, Sarmatians, and Carpi. Aurelian restored the Empire's eastern provinces after his conquest of the Palmyrene Empire in 273. The following year he conquered the Gallic Empire in the west, reuniting the Empire in its entirety. He was also responsible for the construction of the Aurelian Walls in Rome, the abandonment of the province of Dacia, and monetary reform, trying to curb the devaluation of the Roman currency.

Although Domitian, two centuries previous, was the first emperor who had demanded to be officially hailed as dominus et deus ("master and god"), these titles never occurred in written form on official documents until the reign of Aurelian. His successes were instrumental in ending the crisis, earning him the title Restitutor Orbis ("Restorer of the World").