Frederick II (Holy Roman Empire) (1194-1250), Holy Roman emperor (1215-1250) and as Frederick I, king of Sicily (1198-1212).

Born in Lesi, Italy, on December 26, 1194, Frederick was the son of Henry VI and grandson of Frederick I, Holy Roman emperor. He was made German king in 1196 and on the death of his father two years later became king of Sicily. When his mother, Constance of Sicily, acting as regent, died several months later, the four-year-old prince was placed under the guardianship of Pope Innocent III, the new regent of Sicily. Emperor Otto IV was deposed in 1211, and the German princes selected Frederick to replace him. A contest for the imperial throne ensued, because Otto was unwilling to relinquish the crown. Supported by the papacy, to which he promised many concessions, and aided by the French, Frederick was eventually secure in his title. He was crowned king of Germany at Aix-la-Chapelle (now Aachen, Germany) in 1215 and Holy Roman emperor at Rome in 1220. See also Holy Roman Empire.

On his coronation Frederick made a number of elaborate promises to the church, including a vow that he would go on a Crusade. He postponed the Crusade, however, because of an outbreak of anarchy in Sicily and because of the resistance of the Lombard cities, which in 1226 renewed the Lombard League, originally formed against his grandfather, Frederick I. The following year Frederick annulled the Treaty of Constance and put the Lombard cities under the ban of the empire. Threatened several times with excommunication if he did not fulfill his coronation pledge, Frederick determined to sail for Jerusalem in 1227. An epidemic forced him to return three days after his departure, whereupon Pope Gregory IX declared him excommunicated. From 1228 to 1229 Frederick led the Sixth Crusade to the Holy Land. In 1229 he negotiated a treaty to recover Jerusalem and concluded a 10-year truce with the sultan of Egypt. Having married Yolande, the young daughter of the titular king of Jerusalem, John of Brienne, and having assumed his title upon her death, Frederick was crowned king of Jerusalem in that city in 1229.

He returned to Europe and spent many of his remaining years attempting to bring the Lombards under subjection. During intermittent struggles with the papacy he was excommunicated twice again, by Pope Gregory IX in 1239 and in 1245 by Pope Innocent IV. His participation in costly wars in Italy caused him to neglect the welfare of his German subjects. Frederick managed to establish peace, prosperity, and order in Sicily, however, promulgating there in 1231 a comprehensive code of laws, described as the best issued by any Western ruler since the reign of Charlemagne. Frederick also made worthy contributions to learning in Italy. Because he was a man of culture, he gathered scholars and men of letters at his Sicilian court, which Dante called the birthplace of Italian poetry. The University of Naples was founded by Frederick in 1224.

For about a century after his death, on December 13, 1250, the belief persisted that Frederick was still alive. According to one famous legend, Frederick resides in a cave in the Kyffhäuser Mountains, in the region of Thüringen, awaiting the summons of the German people to return and restore peace in the empire. The legend was later interpreted to refer to Frederick I.