Frederick II., a German emperor and king of Naples and Sicily, grandson of the preceding and son of Henry VI. and Constantia of Sicily, born at Jesi, near Ancona, Dec. 26, 1194, died at Fiorentino or at Fiorenzuola, Dec. 13, 1250. He was carefully educated by his mother under the guardianship of Pope Innocent III., acquired an extensive knowledge of ancient and modern languages, and of different sciences, including philosophy, which he learned from a Saracen teacher, and poetry, which he cultivated himself, and soon developed those chival-ric and royal talents, that active, energetic, and buoyant spirit, which made him one of the most distinguished monarchs of the middle ages. He was hereditary duke of Swabia and other dominions in Germany, but for his investiture and coronation as king of Naples and Sicily his mother sacrificed to Innocent III. (1209) some of the most essential rights of the state. His uncle, Philip of Swabia, who disputed the throne of Germany after the death of Henry VI. with Otho IV., having fallen in battle, Frederick was assisted by the pope to reestablish the imperial dignity of his house.

He went to Germany in 1212, was joyfully received by the Ghibellines, compelled Otho to retire, was crowned at Aix-la-Chapelle in 1215, and generally acknowledged in 1218. Leaving his son Henry, whom he caused to be declared king of the Romans, in Germany, he started in 1220 for Italy, hastened to Rome, where he was crowned as emperor, and thence to his hereditary kingdom, whose affairs he arranged while preparing for a crusade, according to a solemn promise given to the see of Rome. Men of science, poets, and artists flocked to his court, the university of Naples was founded, the medical school of Salerno became flourishing, collections of art were procured, and Peter de Vinea prepared an extensive code of laws to suit all the classes and nations of Germany and Italy, which Frederick was scheming to unite into one hereditary empire. These schemes were checked by the independent spirit of the Lombard cities, and by the opposition of the popes Honorius III. and Gregory IX., who finally compelled the emperor, by threats of excommunication, to start upon his long delayed crusade (1227). But a pestilential disease which broke out on board the fleet obliged him to land at Otranto, where the greater part of the pilgrims dispersed.

The expedition only reached the Morea, and Gregory punished the emperor with excommunication and interdict. It was in vain that Frederick started again the next year, reached the Holy Land, and fought successfully against the Mussulmans; the policy of the pope, who declared him unworthy before absolution to battle for the cross, roused against him the patriarch of Jerusalem and the three orders of knights in the East, and also induced his father-in-law, John of Brienne, titular king of Jerusalem and emperor of Constantinople, to invade the Italian kingdom. Having concluded a truce of ten years with the sultan of Egypt, which brought into his possession the holy cities and the whole coast of Judea, he returned as crowned king of Jerusalem, reconquered his kingdom, defeated the intrigues of his enemies, and finally gained his absolution (1230). The Lombard cities still maintained their league, being now supported by the rebellion of Henry, the son of the emperor. Frederick returned to Germany after an absence of 15 years, restored his imperial dignity, and pardoned his son. But a new rebellion drew upon the prince the punishment of imprisonment for life, in the seventh year of which he died.

His younger brother Conrad was made king of the Romans in his stead, and Frederick marched against the Lombards, and defeated them at Cortenuova (Nov. 26-27, 1237); all the cities surrendered except Milan, Brescia, Piacenza, and Bologna, whose resistance was again encouraged by Gregory IX. Irritated by Frederick's having made his natural son Enzio king of Sardinia, the pope again excommunicated the emperor on Palm Sunday, 1239. Frederick marched against Rome, took Ravenna, and had the Genoese fleet, which was conveying 100 prelates to Rome, intercepted by Enzio (1241). Gregory IX. did not long survive these reverses. The short papacy of Celestine IV. and a long interregnum followed, which was terminated by the election of Innocent IV. The new pope, once the friend of the emperor, became his bitterest enemy, confirmed his excommunication, fled to Lyons in France, where he con-voked a council, cited Frederick before this tribunal, rejected his defender Thaddeus of Su-essa, declared the throne of Germany vacant, and subsequently recognized two new emperors, Henry Raspe of Thuringia, who was defeated by Conrad, and William of Holland. The emperor, deserted by many of his allies, lost a battle before Parma, and another near Bologna, in which Enzio was made prisoner. But he continued the struggle until he died.