The Holy Roman Empire was a multi-ethnic complex of territories in central Europe that developed during the Early Middle Ages and continued until its dissolution in 1806. The largest territory of the empire after 962 was the Kingdom of Germany, though it also came to include the Kingdom of Bohemia, the Kingdom of Burgundy, the Kingdom of Italy, and numerous other territories. 

On 25 December 800, Pope Leo III crowned the Frankish king Charlemagne as Emperor, reviving the title in Western Europe, more than three centuries after the fall of the Western Roman Empire. The title continued in the Carolingian family until 888 and from 896 to 899, after which it was contested by the rulers of Italy in a series of civil wars until the death of the last Italian claimant, Berengar, in 924. 

The title was revived in 962 when Otto I was crowned emperor, fashioning himself as the successor of Charlemagne and beginning a continuous existence of the empire for over eight centuries. Some historians refer to the coronation of Charlemagne as the origin of the empire, while others prefer the coronation of Otto I as its beginning. Scholars generally concur, however, in relating an evolution of the institutions and principles constituting the empire, describing a gradual assumption of the imperial title and role.
When did this happen?
The largest territory of the empire after 962 was the Kingdom of Germany,