John VIII - Basileus of Basileía Rhōmaíōn from 1425 to 1448
John VIII was the penultimate reigning Byzantine Emperor, ruling from 1425 to 1448. He as the eldest son of Manuel II Palaiologos and Helena.

John VIII Palaiologos named his brother Constantine XI, who had served as regent in Constantinople in 1437–1439, as his successor. Despite the machinations of his younger brother Demetrios Palaiologos his mother Helena was able to secure Constantine XI's succession in 1448.

John VIII died at Constantinople in 1448, becoming the last reigning Byzantine emperor to die of natural causes.
Emperor John VIII of the Byzantine Empire