Frederick I, byname Frederick Barbarossa (Italian: Redbeard), (born c. 1123—died June 10, 1190), duke of Swabia (as Frederick III, 1147–90) and German king and Holy Roman emperor (1152–90), who challenged papal authority and sought to establish German predominance in western Europe. He engaged in a long struggle with the cities of northern Italy (1154–83), sending six major expeditions southward. He died while on the Third Crusade to the Holy Land.

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Frederick was the son of Frederick II, duke of Swabia, and Judith, daughter of Henry IX, duke of Bavaria, of the rival dynasty of the Welfs. After succeeding his father as duke of Swabia, Frederick was elected German king on March 4, 1152, in Frankfurt, succeeding his uncle, Emperor Conrad III. Frederick’s contemporaries believed that, because he united in himself the blood of the Welfs and the Hohenstaufen, he would solve the internal problems of the kingdom. The announcement of his election, which he sent to Pope Eugenius III, made it plain that Frederick I was not ready to recognize the preeminence over the emperors that the popes had won during the quarrel over the right of investiture of bishops and abbots. Frederick, moreover, filled several vacant episcopal sees, thereby violating the Concordat of Worms of 1122. Nevertheless, he was to learn that he could not prevail against the papacy as easily as the earlier emperors, Otto I and Henry III, had done because the political balance of the West had changed. Under the powerful emperor Manuel I Comnenus, the Byzantine Empire had grown to be a political factor in the Mediterranean and in Italy. Southern Italy and Sicily were united in the Norman kingdom of Roger II. The cities of the Lombards, which had been little more than a nuisance to the earlier emperors, had now become more powerful.