Michael III of Anchialus (Greek: Μιχαὴλ Γ´) was Patriarch of Constantinople from January 1170 to March 1178.
Michael was appointed patriarch by the Byzantine emperor Manuel I Komnenos, culminating what had been a highly distinguished intellectual and administrative career. Before becoming Patriarch, Michael III had held a progression of important church administrative offices, including referendarios, epi tou sakelliou, and protekdikos, the last of which was in charge of the tribunal which adjudicated claims for asylum within the Great Church. The most important of his appointments before receiving the Patriarchal throne was the office of hýpatos tōn philosóphōn (ὕπατος τῶν φιλοσόφων, "chief of the philosophers"), a title given to the head of the imperial University of Constantinople in the 11th–14th centuries. In this role he condemned the neoplatonist philosophers, and encouraged study of Aristotle's work on the natural sciences as an antidote. As Patriarch, Michael III continued to deal with the theological issue of the relation between the Son and the Father in the Holy Trinity. The issue was created due to the explanation that one Demetrius of Lampi (in Phrygia) gave to the phrase of the Gospel of John «ὁ Πατήρ μου μείζων μου ἐστίν», which means my Father is bigger than me (John, XIV.29). Michael acted as the Emperor's chief spokesman on this issue. Michael also ordered a review of Eastern Orthodox ecclesiastical and imperial laws and decrees by Theodore Balsamon known as the "Scholia" (Greek: Σχόλια) (c. 1170).