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.
The Last Legion
The film depicts the coronation of Romulus (and subsequent fall of Rome) as having taken place in 460, while the novel gives the year as 476. In point of fact, coronations were not invented until later in the Roman Empire (in the Byzantine period). Historically, Romulus was a usurper proclaimed by his father in 475. It is believed he was born in 460. Romulus' reign was never recognised as emperor except by his father's troops. The emperors of the East continued to regard Julius Nepos, who had fled Italy and reestablished himself in Dalmatia in the face of a rebellion by Orestes, as the legitimate Western Emperor. Romulus was Emperor for ten months, not a single day as in the film.