The Holy Roman Emperor, originally and officially the Emperor of the Romans (Latin: Imperator Romanorum; German: Kaiser der Römer) during the Middle Ages, and also known as the Roman-German Emperor since the early modern period (Latin: Imperator Germanorum; German: Römisch-Deutscher Kaiser), was the ruler and head of state of the Holy Roman Empire. The title was held in conjunction with the title of King of Italy (Rex Italiae) from the 8th to the 16th century, and, almost without interruption, with the title of King of Germany (Rex Teutonicorum, lit. 'King of the Teutons') throughout the 12th to 18th centuries.
The Holy Roman Emperor title provided the highest prestige among medieval Catholic monarchs, because the empire was considered by the Catholic Church to be the only successor of the Roman Empire during the Middle Ages and the early modern period. Thus, in theory and diplomacy, the emperors were considered primus inter pares—first among equals—among other Catholic monarchs across Europe.
