Marcus Aurelius Antoninus (born Lucius Septimius Bassianus, 4 April 188 – 8 April 217), better known by his nickname Caracalla (/ˌkærəˈkælə/;[3] Latin: [karaˈkalːa]), was Roman emperor from 198 to 217 AD, first serving as nominal co-emperor under his father and then ruling alone after 211 AD. He was a member of the Severan dynasty, the elder son of Emperor Septimius Severus and Empress Julia Domna. Severus proclaimed Caracalla co-ruler in 198, doing the same with his other son Geta in 209. The two brothers briefly shared power after their father's death in 211, but Caracalla soon had Geta murdered by the Praetorian Guard and became sole ruler of the Roman Empire. Julia Domna had a significant share in governance, since Caracalla found administration to be mundane. His reign featured domestic instability and external invasions by the Germanic peoples.
 
At the beginning of 217, Caracalla was still based at Edessa before renewing hostilities against Parthia. On 8 April 217 Caracalla, who had just turned 29, was travelling to visit a temple of the moon god Sin, while on the road from Edessa to Carrhae, now Harran in southern Turkey, where in 53 BC the Romans had suffered a defeat at the hands of the Parthians. After stopping briefly to urinate, Caracalla was approached by a soldier, Justin Martialis, and stabbed. A Scythian bodyguard of Caracalla killed Martialis with his lance. The two Praetorian tribunes rushed to the emperor, as if to help him, and completed the assassination.