Roman emperor
The Western Roman Empire collapsed in the late 5th century. Romulus Augustulus is often considered to be the last emperor of the West after his forced abdication in 476, although Julius Nepos maintained a claim recognized by the Eastern Empire to the title until his death in 480. Following Nepos' death, the Eastern Emperor Zeno abolished the division of the position and proclaimed himself as the sole Emperor of a reunited Roman Empire. The Eastern imperial lineage continued to rule from Constantinople ("New Rome"); they continued to style themselves as Emperor of the Romans (later βασιλεύς Ῥωμαίων in Greek), but are often referred to in modern scholarship as Byzantine emperors. Constantine XI Palaiologos was the last Roman emperor in Constantinople, dying in the Fall of Constantinople to the Ottomans in 1453.
Historiography of the fall of the Western Roman Empire
By the late 5th century the barbarian conqueror Odoacer had no use for the formality of an Empire upon deposing Romulus Augustus and chose neither to assume the title of Emperor himself nor to select a puppet, although legally he kept the lands as a commander of the Eastern Empire and maintained the Roman institutions such as the consulship. The formal end of the Roman Empire on the West in AD 476 thus corresponds with the time in which the Empire and the title Emperor no longer had value.