King of the Two Sicilies, a natural son of the Emperor Frederick II. and of a Lombard lady, was born about 1234. His father dying in 1252, bequeathed to him the principality of Tarentum, and appointed him regent during the absence of his brother Conrad IV. No sooner had Manfredi begun to rule, than the province of Apulia, instigated by Pope Innocent IV., rose in open insurrection. With promptness and vigour he suppressed the rebels; and in the same year in which his government had commenced, delivered into his brother's hands an undisputed sovereignty. He had now become a favourite with the people, but from that very circumstance he was Manfredi, disliked by his brother, and removed from all share in the administration. Yet, in 1254, when the king died, leaving his crown to his infant son Conrad, then in Germany, Manfredi was once more called to the regency. His enjoyment, however, of this dignity was soon interrupted by the inveterate foe of his house, Pope Innocent IV., who forthwith laid him under the ban of excommunication, and, backed by the Guelphs and all the malcontents in the Two Sicilies, advanced to strip him of his power. Deserted by his subjects, and destitute of all means of raising troops, Manfredi was forced to free himself from the sentence of excommunication by agreeing to hold his possessions as an immediate fief of the Holy See. But the pope was unable to rest as long as Manfredi retained any power. Accordingly he began to organize a conspiracy against the liberty and safety of his vassal, which was only frustrated by the latter fleeing from the papal court and repairing for assistance to the Saracens of Lucera, the ever-faithful supporters of his house. With these rallying around him, Manfredi speedily recovered Apulia, and, aided by the death of Pope Innocent IV. in 1254, he received in 1257 the submission of the entire kingdom. In the same year the new pope, Alexander IV., inheriting the hostile spirit of his predecessor, presented the kingdom of the Two Sicilies to Edmund, second son of Henry III. of England, a gift, however, which that prince had not the courage to accept. A report that his nephew Conrad had died in Germany, induced Manfredi in 1258 to assume the title and insignia of king. No sooner had he taken this bold step, than envoys arrived from Conrad's mother to contradict the report, and to demand the resignation of the crown in favour of her son. But Manfredi refused to lay down the sceptre; and so much had his brave defence of his country, his handsome person, and his many accomplishments, endeared him to the hearts of his people, that Conrad's mother was fain to content herself with the promise that her son should be the next occupant of the throne. The elevation of Manfredi only stimulated the enduring enmity of Rome. On the accession of Pope Urban IV. in 1261, he was excommunicated, and his kingdom was placed at the disposal of any European prince who might have the strength to make it his own. At last Charles, Count of Anjou, and brother to Louis IX. of France, accepted the offer; but no sooner had he concluded the bargain with the Roman See than Urban died in 1264. Pope Clement IV. assumed the policy of his predecessor, and after crowning the Count of Anjou with great solemnity, sent him forth in January 1266 against the kingdom of the Two Sicilies. Manfredi, in the February following, encountered the enemy at Benevento. The Apuliens passing over to the invaders at a critical moment in the fight, threw the entire Sicilian army into disorder. Manfredi, on seeing the desperate nature of his cause, spurred into the thickest of the battle, and fell covered with wounds. His mangled body was buried under a heap of stones; but ecclesiastical enmity, denying it even this poor resting-place, ordered it to be dragged out and conveyed to a barren valley on the confines of Abruzzo. There, in accordance with the sentence of excommunication, it was interred without any burial rites. Manfredi was the founder of the town of Manfredonia.

Manfredi, Eustachio, an eminent mathematician and astronomer, was born in 1674 at Bologna in Italy. At first he studied philosophy and jurisprudence, and evinced a strong love for poetry, but latterly he devoted most of his time to mathematics and astronomy. He was appointed mathematical professor in the university of his native city in 1693, and surveyor-general of the rivers and waters in 1704. He was chosen regent of Montalto College during the same year, an office which he resigned in 1711 for that of astronomer to the newly established Institute of Bologna. Manfredi was chosen a foreign member of the Academy of Sciences at Paris, and of the Royal Society of London. He died of the stone in 1739. The principal of Manfredi's works are,—Ephemerides Motuum Coelestium ab anno 1715 ad annum 1750, in 4 vols. 4to; De Transitu Mercurii per solen anno 1723, 4to, Bologna, 1724; and De annuis Inerrantium Stellarum Aberrationibus, 4to, Bologna, 1729.