Constantine Mesopotamites () was a senior Byzantine official, and "de facto" chief minister under the emperors Isaac II Angelos and Alexios III Angelos from 1193 until his fall in summer 1197. He was also archbishop of Thessalonica from until , but was in exile between 1204 and 1224, when the city was occupied by Latin Crusaders. Restored to his see, he refused to crown Theodore Komnenos Doukas as emperor, and departed his see again in self-exile. He was also a colleague and correspondent of the historian Niketas Choniates, and may have commissioned some of the latter's works.