John VI Kantakouzenos or Cantacuzene (, Iōánnēs Ángelos Palaiológos Kantakouzēnós; ; – 15 June 1383) was a Byzantine Greek nobleman, statesman, and general. He served as grand domestic under Andronikos III Palaiologos and regent for John V Palaiologos before reigning as Byzantine emperor in his own right from 1347 to 1354. Deposed by his former ward, he was forced to retire to a monastery under the name and spent the remainder of his life as a monk and historian. At age 90 or 91 at his death, he was the longest-lived of the Roman emperors. Early life Born in Constantinople, John Kantakouzenos was the son of Michael Kantakouzenos, governor of the Morea; Donald Nicol speculates that he may have been born after his father's death and raised as an only child. Through his mother Theodora Palaiologina Angelina, he was related to the then-reigning house of Palaiologos. He was also related to the imperial dynasty through his wife Irene Asanina, a second cousin of Emperor Andronikos III Palaiologos. Kantakouzenos became a close friend to Andronikos III and was one of his principal supporters in Andronikos's struggle against his grandfather, Andronikos II Palaiologos. On the accession of Andronikos III in 1328, he was entrusted with the supreme administration of affairs and served as grand domestic throughout his reign. He was named regent to Andronikos's successor, the 9-year-old John V, upon the emperor's death in June 1341. Kantakouzenos apparently began with no imperial ambitions of his own, having refused several times to be crowned co-emperor by Andronikos III. After the death of the emperor, Kantakouzenos again refused to take the throne, insisting on the legitimacy of John V's claim and contenting himself with overseeing the empire's administration until the boy came of age: according to the history written by John VI himself. Whether he would have remained loyal is unknowable but, despite his professed devotion to John V and his mother Anna, she came to suspect him of treason. His close friendship with the late emperor and power over his successor had aroused the jealousy of his former protégés, Patriarch John XIV of Constantinople and Alexios Apokaukos; after a series of failed attempts, they succeeded in overthrowing his regency in September 1341 while he was out of the capital readying an army against the Crusader principalities that still held parts of the Peloponnesus. He attempted to negotiate with the usurpers, but this was