Mesazon

thumb|250px|Mosaic portraying Theodore Metochites (left), to Emperor [[Andronikos II Palaiologos (), presenting the model of the renovated Chora Church to Christ Pantocrator.]] The ' () was a high dignitary and official during the last centuries of the Byzantine Empire, who acted as the chief minister and principal aide of the Byzantine emperor. In the West, the dignity was understood as being that of the imperial chancellor' ().

==History and functions== The term's origins lie in the 10th century, when senior ministers were sometimes referred to as the (), i.e. 'mediators' between the emperor and his subjects (cf. ). The title first became official in the mid-11th century, when it was conferred on Constantine Leichoudes, the future ecumenical patriarch of Constantinople. In the Komnenian period, it was awarded to senior government officials who functioned as de facto prime ministers, such as the and the , but had not yet acquired a permanent and specific function, nor the power that would characterize it in later years. Rather, it was a title bestowed on the principal imperial secretary of the moment, who acted precisely as an "intermediary" between the emperor and other officials. This reflected the shift of the Byzantine government under the Komnenoi from the old Roman-style bureaucracy to a more restricted, aristocratic ruling class, where government was exercised within the imperial household, as in feudal Western Europe.