Holy Roman Empire
The empire was dissolved on 6 August 1806, when the last Holy Roman Emperor Francis II (from 1804, Emperor Francis I of Austria) abdicated, following a military defeat by the French under Napoleon at Austerlitz (see Treaty of Pressburg). Napoleon reorganized much of the Empire into the Confederation of the Rhine, a French satellite. Francis' House of Habsburg-Lorraine survived the demise of the empire, continuing to reign as Emperors of Austria and Kings of Hungary until the Habsburg empire's final dissolution in 1918 in the aftermath of World War I.
Constantine VI
Constantine VI was the final ruler to be universally recognized as Roman Emperor, being recognized as such by both the Empire which he ruled in the east, the papacy and the Western European powers over which the pope held suzerainty. With his mother becoming Empress regnant upon his deposition, the papacy crowned Charlemagne as a new Emperor in Western Europe, asserting that a woman could not be Empress in her own right. This laid the foundations of a new polity, independent of the East, that would evolve into the "Holy Roman Empire".