From about 1 February, 772, till 25 December, 795; date of birth uncertain; d. 25 December, 795. His pontificate of twenty-three years, ten months, and twenty-four days was unequalled in length by that of any successor of St. Peter until a thousand years later, when Pius VI, deposed and imprisoned by the same Frankish arms which had enthroned the first Pope-King, surpassed Adrian by a pontificate six months longer. At a critical period in the history of the Papacy, Adrian possessed all the qualities essential in the founder of a new dynasty. He was a Roman of noble extraction and majestic stature. By a life of singular piety, by accomplishments deemed extraordinary in that iron age, and by valuable services rendered during the pontificate of Paul I and Stephen III, he had so gained the esteem of his unruly countrymen that the powerful chamberlain, Paul Afiarta, who represented in Rome the interests of Desiderius, the Lombard king, was powerless to resist the unanimous voice of the clergy and people demanding for Adrian the papal chair. The new pontiff's temporal policy was, from the first, sharply defined and tenaciously adhered to; the keynote was a steadfast resistance to Lombard aggression. He released from prison or recalled from exile the numerous victims of the chamberlain's violence; and, upon discovering that Afiarta had caused Sergius, a high official of the papal court, to be assassinated in prison, ordered his arrest in Rimini, just as Afiarta was returning from an embassy to Desiderius with the avowed intention of bringing the Pope to the Lombard court, "were it even in chains." The time seemed propitious for subjecting all Italy to the Lombard rule; and with less able antagonists than Adrian and Charles (to be famous in later ages as Charlemagne), most probably the ambition of Desiderius would have been gratified. There seemed little prospect of Frankish intervention. The Lombards held the passes of the Alps, and Charles was engrossed by the difficulties of the Saxon war; moreover, the presence in Pavia of Gerberga and her two sons, the widow and orphans of Carloman, whose territories, on his brother's death, Charles had annexed, seemed to offer an excellent opportunity of stirring up discord among the Franks, if only the Pope could be persuaded, or coerced, to anoint the children as heirs to their father's throne. Instead of complying, Adrian valiantly determined upon resistance. He strengthened the fortifications of Rome, called to the aid of the militia the inhabitants of the surrounding territory, and, as the Lombard host advanced, ravaging and plundering summoned Charles to hasten to the defence of their common interests. An opportune lull in the Saxon war left the great commander free to act. Unable to bring the deceitful Lombard to terms by peaceful overtures, he scaled the Alps in the autumn of 773, seized Verona, where Gerberga and her sons had sought refuge, and besieged Desiderius in his capital. The following spring, leaving his army to prosecute the siege of Pavia, he proceeded with a strong detachment to Rome, in order to celebrate the festival of Easter at the tomb of the Apostles. Arriving on Holy Saturday, he was received by Adrian and the Romans with the utmost solemnity. The next three days were devoted to religious rites; the following Wednesday to affairs of state. The enduring outcome of their momentous meeting was the famous "Donation of Charlemagne", for eleven centuries the Magna Charta of the temporal power of the Popes. (See CHARLEMAGNE.) Duchesne's thorough and impartial investigation of its authenticity in his edition of the Liber Pontificalis (I, ccxxxv-ccxliii) would seem to have dissipated any reasonable doubt. Two months later Pavia fell into the hands of Charles; the kingdom of the Lombards was extinguished, and the Papacy was forever delivered from its persistent and hereditary foe. Nominally, Adrian was now monarch of above two-thirds of the Italian peninsula; but his sway was little more than nominal. Over a great portion of the district mentioned in the Donation, the papal claims were permitted to lapse. To gain and regain the rest, Charles was forced to make repeated expeditions across the Alps. We may well doubt whether the great King of the Franks would have suffered the difficulties of the Pope to interfere with his more immediate cares, were it not for his extreme personal veneration of Adrian, whom in life and death he never ceased to proclaim his father and best friend It was in no slight degree owing to Adrian's political sagacity, vigilance, and activity, that the temporal power of the Papacy did not remain a fiction of the imagination.
His merits were equally great in the more spiritual concerns of the Church. In cooperation with the orthodox Empress Irene, he laboured to repair the damages wrought by the Iconoclastic storms. In the year 787 he presided, through his legates, over the Seventh General Council, held at Nicaea, in which the Catholic doctrine regarding the use and veneration of images was definitely expounded. The importance of the temporary opposition to the decrees of the Council throughout the West, caused mainly by a defective translation, aggravated by political motives, has been greatly exaggerated in modern times. The controversy elicited a strong refutation of the so-called Libri Carolini from Pope Adrian and occasioned no diminution of friendship between him and Charles. He opposed most vigorously, by synods and writings, the nascent heresy of Adoptionism (q.v.), one of the few Christological errors originated by the West. The Liber Pontificalis enlarges upon his merits in embellishing the city of Rome, upon which he is said to have expended fabulous sums. He died universally regretted, and was buried in St. Peter's. His epitaph, ascribed to his lifelong friend, Charlemagne, is still extant. Rarely have the priesthood and the empire worked together so harmoniously, and with such beneficent results to the Church and to humanity, as during the lifetime of these two great rulers. The chief sources of our information as to Adrian are the Life in the Liber Pontificalis (q.v.), and his letters to Charlemagne, preserved by the latter in his Codex Carolinus. Estimates of Adrian's work and character by modern historians differ with the varying views of writers regarding the temporal sovereignty of the popes, of which Adrian I must be considered the real founder.
Liber Pontificalis (ed. DUCHESNE), I, 486-523, and praef. CCXXXIV sq.; ID., Les premiers ternps de l'état pontifical (Paris, 1898); JAFF , Regesta RR. PP. (2d ed.), I, 289-306, Il. 701; ID., Bibl. Rer. Germanic. (Codicis Carol. Epistolae), IV, 13-306; CENNI, Monum. dominat. pontif. (1761), II, 289-316, also in P.L. XCVIII; MANN, The Lives of the Popes in the Early Middle Ages (London, 1902), I, II, 395-496; HEFELE, History of the Councils (tr.), III, passim; NIEHUES, Gesch. d. Verh ltnisses zwischen dem Kaiserthum u. Papsthum im Mittelalter (Munster, 1877), I, 517-546; GOSSELIN, Power of the Pope in the Middle Ages (Baltimore, 1853), I, 230 sq.; SCHN RER, Entstehung des Kirchenstaates (Cologne, 1894). For a bibliography of Adrian I see CHEVALIER, Bio-Bibliogr. (2d ed., Paris, 1905), 55, 56.
JAMES F. LOUGHLIN