Coats of arms of prince electors surround the Holy Roman Emperor's; from flags book of Jacob Köbel (1545). Electors voted in an Imperial Diet for a new Holy Roman Emperor.
From the time of
Constantine I (4th century) the
Roman emperors had, with very few exceptions, taken on a role as promoters and defenders of
Christianity. The title of Emperor became defunct in
Western Europe after the deposition of
Romulus Augustulus in AD 476, although the rulers of the "
barbarian kingdoms" continued to recognize the
Eastern Emperor at least nominally well into the 6th century; both the title and connection between Emperor and
Church continued in the
Eastern Roman Empire until 1453, when it fell to the forces of the
In the west, the title of Emperor (Imperator) was revived in 800, which also renewed ideas of imperial–papal cooperation. As the power of the papacy grew during the Middle Ages, popes and emperors came into conflict over church administration. The best-known and most bitter conflict was that known as the
Investiture Controversy, fought during the 11th century between
Henry IV and
Pope Gregory VII.
Charlemagne was crowned Emperor of the Romans (Imperator Romanorum) by
Pope Leo III, his successors maintained the title until the death of
Berengar I of Italy in 924. No pope appointed an emperor again until the coronation of
Otto the Great in 962. Under Otto and his successors, much of the former
Carolingian kingdom of
Eastern Francia fell within the boundaries of the Holy Roman Empire. The various
German princes elected one of their peers as
King of the Germans, after which he would be crowned as emperor by the
Pope. After Charles V's coronation, all succeeding emperors were called elected Emperor due to the lack of papal coronation, but for all practical purposes they were simply called emperors.
The term "sacrum" (i.e. "holy") in connection with the medieval Roman Empire was first used in 1157 under
Frederick I Barbarossa.
Charles V was the last Holy Roman Emperor to be crowned by the Pope (1530). The final Holy Roman Emperor-elect,
Francis II, abdicated in 1806 during the
Napoleonic Wars that saw the Empire's final dissolution.
The standard designation of the Holy Roman Emperor was "August Emperor of the Romans" (Romanorum Imperator Augustus). When Charlemagne was crowned in 800, he was styled as "most serene Augustus, crowned by God, great and pacific emperor, governing the Roman Empire," thus constituting the elements of "Holy" and "Roman" in the imperial title. The word Holy had never been used as part of that title in official documents.
The word Roman was a reflection of the principle of
translatio imperii (or in this case
restauratio imperii) that regarded the (Germanic) Holy Roman Emperors as the inheritors of the title of Emperor of the
Western Roman Empire, despite the continued existence of the Eastern Roman Empire. In German-language historiography, the term Römisch-deutscher Kaiser ("Roman-German emperor") is used to distinguish the title from that of
Roman Emperor on one hand, and that of
German Emperor (Deutscher Kaiser) on the other. The English term "Holy Roman Emperor" is a modern shorthand for "emperor of the Holy Roman Empire" not corresponding to the historical style or title.