Thomas Palaiologos was Despot of the Morea from 1428 until the fall of the despotate in 1460, although he continued to claim the title until his death five years later. He was the younger brother of Constantine XI Palaiologos, the final Byzantine emperor. Thomas was appointed as Despot of the Morea by his oldest brother, Emperor John VIII Palaiologos, in 1428, joining his two brothers and other despots Theodore and Constantine, already governing the Morea. Though Theodore proved reluctant to cooperate with his brothers, Thomas and Constantine successfully worked to strengthen the despotate and expand its borders. In 1432, Thomas brought the remaining territories of the Latin Principality of Achaea, established during the Fourth Crusade more than two hundred years earlier, into Byzantine hands by marrying Catherine Zaccaria, heiress to the principality.

Constantine XI Dragases Palaiologos or Dragaš Palaeologus was the last Roman (Byzantine) emperor, reigning from 1449 until his death in battle at the Fall of Constantinople in 1453. Constantine's death marked the definitive end of the Eastern Roman Empire, which traced its origin to Constantine the Great's foundation of Constantinople as the Roman Empire's new capital in 330.