CÆSAR, in Roman Antiquity, a title borne by all the emperors, from the time of Julius Cæsar till the destruction of the empire. It was also used as a title of distinction for the intended or presumptive heir of the empire; as King of the Romans was latterly used for that of the German empire.
This title took its rise from the surname of C. Julius Cæsar, which, by a decree of the senate, all the succeeding emperors were to bear. Under his successor, the appellation of Augustus being appropriated to the emperors in compliment to the prince of that name, the title Cæsar was given to the second person in the empire, though still it continued to be used by the first; and hence the difference between Cæsar used simply, and Cæsar with the addition of Imperator Augustus.
The title of Cæsar was allotted to the second personage of the empire, till Alexius Comnenus found it necessary, in consequence of having elected Nicephorus Melissenus Cæsar by contract, to confer some higher dignity on his own brother Isaacus. He created him Sebastocrator, with the precedence over Melissenus; ordering that in all proclamations Isaacus Sebastocrator should be named the second, and Melissenus Cæsar the third.