Marcus Opellius Macrinus (ca. 165 - June 218) was Roman emperor for fourteen months in 217 and 218. Macrinus was the first emperor to become so without membership in the senatorial class and the first emperor of Berber descent.
In the spring of 217, Caracalla was in the eastern provinces preparing a campaign against the Parthian Empire. Macrinus was among his staff, as were other members of the praetorian guard. In April, the emperor went to visit a temple of Luna near the spot of the battle of Carrhae, accompanied only by his personal bodyguard, which included Macrinus. Events are not clear, but it is certain that Caracalla was murdered at some point on the trip (perhaps on April 8). Caracalla's body was brought back from the temple by his bodyguards, along with the corpse of a fellow bodyguard. The story as told by Macrinus was that the dead guard had killed Caracalla. By April 11, Macrinus proclaimed himself emperor. Macrinus also nominated his son Diadumenianus Caesar and successor and conferred upon him the name "Antoninus", thus connecting him with the relatively stable reigns of the Antonine emperors of the 2nd century.
In urgent matters of foreign policy, Macrinus displayed a tendency towards conciliation and a reluctance to engage in military conflict. He averted trouble in the province of Dacia by returning hostages that had been held by Caracalla, and he ended troubles in Armenia by granting that country's throne to Tiridates, whose father had also been imprisoned under Caracalla. Less easily managed was the problem of Mesopotamia, which had been invaded by the Parthians in the wake of Caracalla's demise. Meeting the Parthians in battle during the summer of 217, Macrinus achieved a costly draw near the town of Nisibis and as a result was forced to enter negotiations through which was obliged to pay the enormous indemnity of 200 million sesterces to the Parthian ruler Artabanus IV in return for peace.
Macrinus' reluctance to engage in warfare, and his failure to gain victory over even a historically inferior enemy such as the Parthians caused considerable resentment among the soldiers. This was compounded by the rolling back of the privileges they had enjoyed under Caracalla and the introduction of a pay system by which recruits received less than veterans. After only a short while, the legions were searching for a rival emperor.
His popularity also suffered in Rome. Not only had the new emperor failed to visit the city after taking power, but a late-summer thunderstorm caused widespread fires and flooding, and Macrinus' appointee as urban prefect proved unable to repair the damage to the satisfaction of the populace and had to be replaced.
On May 18, Elagabalus was proclaimed emperor by the Legio III Gallica at its camp at Raphana. A force under his tutor Gannys marched on Antioch and engaged a force under Macrinus on June 8 218. Macrinus, deserted by most of his soldiers, was soundly defeated in the battle, and fled towards Italy disguised as a courier. He was captured near Chalcedon and later executed in Cappadocia. His son Diadumenianus, sent for safety to the Parthian court, was captured at Zeugma and also put to death.
Macrinus' short reign, while important for its historical "firsts", was cut short due to the inability of this otherwise accomplished man to control or satisfy the soldiery. In his death at the hands of Roman soldiers, Macrinus reinforced the notion of the soldiers as the true brokers of power in the 3rd century empire and highlighted the importance of maintaining the support of this vital faction. His reign was followed by another seventeen years of rule under the Severan emperors Elagabalus and Severus Alexander.