Charlemagne was crowned Emperor of the Romans in 800.
Pope Leo III crowned Charlemagne in St. Peter's Basilica in Rome on Christmas Day, 25 December 800. The ceremony revived the western imperial title more than three centuries after the deposition of Romulus Augustulus in 476. Charlemagne was already king of the Franks and king of the Lombards, and the coronation recognized the extraordinary power he had accumulated across western and central Europe.
The event was also a major political statement. The Byzantine Empire, whose ruler in Constantinople claimed the Roman imperial legacy, did not immediately accept Charlemagne's title. Historians still debate whether Charlemagne expected the coronation, how much he planned it, and whether he regarded the title as a new western empire or as recognition of authority he already exercised.
The year 814 is a common trap because Charlemagne died then, while 799 was the year before Leo III sought his protection after political opponents attacked him. Charlemagne's imperial reign is conventionally dated from 800 to 814, although the later Holy Roman Empire is often traced more narrowly to Otto I's coronation in 962.