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.
House of Habsburg
After the death of his father in 1493, Maximilian was proclaimed the new King of the Romans, receiving the name Maximilian I. Maximilian was initially unable to travel to Rome to receive the Imperial title from the Pope, due to opposition from Venice and from the French who were occupying Milan, as well a refusal from the Pope due to enemy forces being present on his territory. In 1508, Maximilian proclaimed himself as the "chosen Emperor," and this was also recognized by the Pope due to changes in political alliances. This had a historical consequence in that, in the future, the Roman King would also automatically become Emperor, without needing the Pope's consent. In 1530, Emperor Charles V became the last person to be crowned as the Emperor by the Pope.