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.
Francis II, Holy Roman Emperor
Francis II (; 12 February 1768 – 2 March 1835) was the last Holy Roman Emperor, ruling from 1792 until 6 August 1806, when he dissolved the Holy Roman Empire of the German Nation after the decisive defeat at the hands of the First French Empire led by Napoleon at the Battle of Austerlitz. In 1804, he had founded the Austrian Empire and became Francis I, the first Emperor of Austria, ruling from 1804 to 1835, so later he was named the one and only "Doppelkaiser" (double emperor) in history.
For the two years between 1804 and 1806, Francis used the title and style "by the Grace of God elected Roman Emperor, ever Augustus, hereditary Emperor of Austria" and he was called the "Emperor of both the Holy Roman Empire and Austria". He was also Apostolic King of Hungary and Bohemia as Francis I. He also served as the first president of the German Confederation following its establishment in 1815.