The ordo senatorius, the senatorial class, was the highest social class in Early Byzantium. It was made up of citizens who, as members of the senate of Constantinople (that is, as successors of the Roman senate, in the Eastern Roman Empire) theoretically took part in the government of the Empire. The main criteria for admittance into the Roman senate had been aristocratic origin and wealth, although emperors could appoint people who fell into neither of these categories but who had distinguished themselves in such high-ranking offices as that of clarissimus (Gr: lambrotatos), spectabilis (Gr: peribleptos) or illustris (Gr: endoxou-illoustriou). The latter criterion gradually prevailed in the eastern part of the Empire, as the institution was still new here and emperors made an effort to create a new imperial aristocracy, and became the main route for being admitted into the senate of Constantinople. In fact, the policy of the Early Byzantine emperors invested the senate of Constantinople with a prestige equal to that of the Roman senate, with the result that there was a constant increase of supreme honorary titles that allowed one to become a member of the senate. Former state employees as well as eminent literary or scientific figures (doctors, mechanics and architects) who did not possess such high offices could also be awarded these titles. Finally, a significant number of curiales (Gr: bouleuai) had 'infiltrated' into the senate despite occasional regulations against it.

Of all senators in possession of such titles, only the illustrii had the actual right to participate in the proceedings of the senate. They were permanent residents of Constantinople, while the rest lived in the provinces. Provincial administrators were recruited from their ranks. In this manner, there was a conflict in the Roman state between the institution of the senate as a consultative body and the supreme tool of public administration on the one hand, and the wider group of senators on the other. The latter were now simply a homogenized aristocratic social class, despite further stratification within their class on the basis of wealth and title.