Magister officiorum

The magister officiorum (Latin literally for "Master of Offices", in Greek: μάγιστρος τῶν ὀφφικίων, romanized: magistros tōn offikiōn) was one of the most senior administrative officials in the Later Roman Empire and the early centuries of the Byzantine Empire. In Byzantium, the office was eventually transformed into a senior honorary rank, simply called magistros (μάγιστρος), until it disappeared in the 12th century.