(Ματθαῖος ὁ Καντακουζήνος), co-emperor of Constantinople, was the eldest son of John VI., who associated him in the supreme government in 1359, with a view of thwarting the schemes of John Palaeologus, who, although then an exile in Tenedos, enjoyed great popularity, and had a fair prospect of seizing the throne. Both John and Matthaeus, however, were unable to prevent John Palaeologus from taking Constantinople in the month of January, 1355, an event which put an end at once to the reign of the father and the son, who both abdicated and retired into a convent. [JOANNES VI.] Matthaeus, who died before his father, or towards the end of the 14th century, was married to Irene Palaeologina, by whom he had six children. [See CANTACUZENUS, genealogical table.]