The Byzantine civil war of 1341–1347 formally begins with the proclamation of John VI Kantakouzenos as Byzantine Emperor.

The Byzantine civil war of 1341–1347, sometimes referred to as the Second Palaiologan Civil War, was a conflict that broke out in the Byzantine Empire after the death of Andronikos III Palaiologos over the guardianship of his nine-year-old son and heir, John V Palaiologos. It pitted on the one hand Andronikos III's chief minister, John VI Kantakouzenos, and on the other a regency headed by the Empress-Dowager Anna of Savoy, the Patriarch of Constantinople John XIV Kalekas, and the megas doux Alexios Apokaukos. The war polarized Byzantine society along class lines, with the aristocracy backing Kantakouzenos and the lower and middle classes supporting the regency. To a lesser extent, the conflict acquired religious overtones; Byzantium was embroiled in the Hesychast controversy, and adherence to the mystical doctrine of Hesychasm was often equated with support for Kantakouzenos.

John VI Kantakouzenos or Cantacuzene 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 Joasaph Christodoulos 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.

The foundation of Constantinople in 330 AD marks the conventional start of the Eastern Roman Empire, which fell to the Ottoman Empire in 1453 AD. Only the emperors who were recognized as legitimate rulers and exercised sovereign authority are included, to the exclusion of junior co-emperors who never attained the status of sole or senior ruler, as well as of the various usurpers or rebels who claimed the imperial title.