Frederick Barbarossa, also known as Frederick I, was the Holy Roman Emperor from 1155 until his death 35 years later in 1190. He was elected King of Germany in Frankfurt on 4 March 1152 and crowned in Aachen on 9 March 1152. He was crowned King of Italy on 24 April 1155 in Pavia and emperor by Pope Adrian IV on 18 June 1155 in Rome. Two years later, the term sacrum ("holy") first appeared in a document in connection with his empire. He was later formally crowned King of Burgundy, at Arles on 30 June 1178. He was named Barbarossa by the northern Italian cities which he attempted to rule: Barbarossa means "red beard" in Italian; in German, he was known as Kaiser Rotbart, which in English means "Emperor Redbeard." The prevalence of the Italian nickname, even in later German usage, reflects the centrality of the Italian campaigns to his career.

The Holy Roman Emperor, originally and officially the Emperor of the Romans during the Middle Ages, and also known as the Roman-German Emperor since the early modern period, 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 from the 8th to the 16th century, and, almost without interruption, with the title of king of Germany throughout the 12th to 18th centuries.