Foundation
The Holy Roman Empire was conventionally founded on Christmas Day 800 AD when Pope Leo III crowned the Frankish king Charlemagne as emperor of the Romans in St Peter’s Basilica in Rome. The coronation revived the title of Roman emperor in western Europe — extinct since the deposition of Romulus Augustulus in 476 — and claimed the political continuity of the Roman state for the new Frankish-papal alliance. The Byzantine Empire at Constantinople, which had continuously possessed the Roman imperial title since the 4th century, was outraged but unable to prevent it.
Charlemagne’s empire was partitioned among his grandsons by the Treaty of Verdun (843) and was no longer a coherent political entity by the late 9th century. The Holy Roman Empire as a continuous institution is therefore sometimes dated instead from the coronation of Otto I in Rome on 2 February 962, which reconstituted the imperial title under the East Frankish (German) monarchy.
The medieval empire
The medieval Holy Roman Empire was an elective rather than hereditary monarchy. The emperor was chosen by the senior territorial princes of the empire — a group formalized by the Golden Bull of 1356 as seven prince-electors: the three Rhenish archbishops (Mainz, Cologne, Trier), the King of Bohemia, the Count Palatine of the Rhine, the Duke of Saxony, and the Margrave of Brandenburg. The election produced a King of the Romans who became emperor only after a papal coronation in Rome (a requirement that lapsed in the late medieval period).
Emperor and pope were the two universalist authorities of medieval Latin Christendom and frequently in conflict over questions of investiture, taxation, and ecclesiastical appointment. The Investiture Controversy (1075–1122) — over whether secular rulers could appoint bishops — was the most intense of these conflicts; it produced the Walk to Canossa (1077), the various papal excommunications of Henry IV, and the eventual Concordat of Worms (1122). The conflict recurred in attenuated forms through the medieval period.
The empire’s territorial extent at peak (12th century) encompassed approximately 1.1 million square kilometres of modern Germany, Austria, Czechia, Switzerland, the Netherlands, Belgium, Luxembourg, Slovenia, eastern France, and northern Italy. The Italian territories were progressively lost during the late medieval period.
The early modern empire
The Habsburg dynasty held the imperial title almost continuously from 1438 to 1806. The Reformation of the 16th century permanently divided the empire into Catholic and Protestant territories; the Peace of Augsburg (1555) regulated the religious settlement on the principle of cuius regio, eius religio (whoever’s region, his religion). The Thirty Years’ War (1618–1648) effectively destroyed the empire’s central political institutions and confirmed the territorial sovereignty of its constituent states at the Peace of Westphalia.
After 1648 the Holy Roman Empire was less a state than a complex network of approximately 1,800 (later 1,500) territorial polities — kingdoms, principalities, ecclesiastical states, free cities, knightly territories, and others — held together by shared imperial law (the Reichsrecht), the imperial supreme court (the Reichskammergericht), and the (declining) imperial diet (the Reichstag) at Regensburg. Voltaire’s famous quip in the 18th century — that the empire was “neither holy, nor Roman, nor an empire” — captured the political situation.
Dissolution
The empire was destroyed by Napoleon’s campaigns of the early 19th century. The French invasion of 1796 and the Reichsdeputationshauptschluss of 1803 reorganized the territorial map. After Napoleon’s decisive defeat of Austria at Austerlitz in December 1805 and the Treaty of Pressburg, sixteen southern and western German states left the empire to form the French-protected Confederation of the Rhine. The Habsburg emperor Francis II abdicated the imperial title and dissolved the empire on 6 August 1806. The empire had existed for 1,006 years on the Otto reckoning or 844 years if dissolution is counted as the end-point.
Successors
The Holy Roman Empire’s institutional legacy was inherited piecemeal. The Habsburg dynasty continued to rule the Austrian Empire (formed in 1804 in anticipation of the imperial title’s loss) and later the Austro-Hungarian Empire until 1918. The remaining German territories were reorganized through the German Confederation (1815–1866), the North German Confederation (1867–1871), and Bismarck’s German Empire (1871–1918). Modern Germany, Austria, the Czech Republic, and several smaller countries inherit substantial parts of the Holy Roman political tradition.
The empire’s medieval imperial regalia (the Imperial Crown, the Holy Lance, the Imperial Sword) are preserved in Vienna’s Imperial Treasury and the Cathedral Treasury of Aachen.