Caracalla (April 4, 186 - April 8, 217) was emperor of the Roman Empire from AD 211 - 217.
Born in Lyons in the province of Gaul in 186, he was the son of the future emperor Septimius Severus and Julia Domna. His given name was Marcus Aurelius Antoninus, but he adopted the name Caracalla, which referred to the hooded tunic worn by his fellow-countrymen.
Severus, who had taken the imperial throne in 193, died in 211 while visiting Eboracum (York), and Caracalla was proclaimed co-emperor with his brother Publius Septimius Antoninius Geta. Caracalla killed Geta and carried out a vendetta against Geta's supporters, in order to strengthen his own hold on power. When the inhabitants of Alexandria heard Caracalla's claims that he had killed Geta in self-defense, they produced a satire mocking this claim, as well as Caracalla's other pretensions. Caracalla responded to this insult savagely in 215 by slaughtering the deputation of leading citizens who had unsuspectingly assembled before the city to greet his arrival, then unleashed his troops for several days of looting and plunder of Alexandria. According to Cassius Dio, Caracalla slaughtered some 20,000 people during his reign.
Geoffrey of Monmouth lists Caracalla, named Bassianus in the Historia Regum Britanniae, as one of the kings of Britain following the death of Geta. This is partially true as Geta was established as emperor more strongly in the west and when he was killed, Caracalla probably exerted his power of the Britons as well. In this account, Caracalla is listed as a half-brother of Geta through a Briton mother. This claim is highly criticized by historians. The text goes on to say that a warrior named Carausius was given ships to defend the British coastline and instead he rose up and defeated Caracalla. It never states that Caracalla was killed in this battle but it does say that Caracalla fled from it. After this point in time, Roman rule weakened considerably in Britain until it was restored with Constantius Chlorus.
Three things stand out from his reign: the edict of 212 (Constitutio Antoniniana) granting Roman citizenship to freemen throughout the Roman Empire; debasing the silver content in Roman coinage by 25%; and the construction of a large thermae outside Rome, the remains of which, known as the Baths of Caracalla, can still be seen.
Caracalla had effectively become a military dictator, and was consequently very unpopular except with the soldiers. While travelling from Edessa to begin a war with Parthia, he was assassinated near Harran on April 8, 217 by Martialis. He was succeeded by the Prefect of the guard, Macrinus.