Translatio imperii

The term translatio imperii, Latin for "transfer of rule", refers to the passing of the crown of the emperor to the Holy Roman Empire when, in 800, Charlemagne, king of the Franks, and then in 962, Otto I the Great, king of the East Franks, was crowned emperor by the pope in Rome.

The mythical background was that there could ever be only one Empire, and there only ever was one. It was considered to have started with Alexander the Great, having been turned over to the Romans, then to the Franks, and finally to the Holy Roman Empire (and this explains the Roman component of the Empire's name). The German emperors thus thought of themselves as being in direct succession of those of the Roman empire.