Aurelian ( Lucius Domitius Aurelianus; 9 September c. 214 – c. November 275) was a Roman emperor, who reigned during the Crisis of the Third Century, 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 modest circumstances, most likely in Moesia Superior, he entered the Roman army in 235 and climbed up the ranks. He went on to lead the cavalry of the emperor Gallienus, until Gallienus' assassination in 268. Following that, 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 earlier, 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").

The deaths of the Sassanid Kings Shapur I (272) and Hormizd I (273) in quick succession, and the rise to power of a weakened ruler (Bahram I), presented an opportunity to attack the Sassanid Empire, and in 275 Aurelian set out for another campaign against the Sassanids. On his way, he suppressed a revolt in Gaul – possibly against Faustinus, an officer or usurper of Tetricus – and defeated barbarian marauders in Vindelicia (Germany).

However, Aurelian never reached Persia, as he was murdered while waiting in Thrace to cross into Asia Minor. As an administrator, he had been strict and had handed out severe punishments to corrupt officials or soldiers. A secretary of his (called Eros by Zosimus) had told a lie on a minor issue. In fear of what the emperor might do, he forged a document listing the names of high officials marked by the emperor for execution and showed it to collaborators. The notarius Mucapor and other high-ranking officers of the Praetorian Guard, fearing punishment from the emperor, murdered Aurelianus shortly after October 275 in Caenophrurium, Thrace.