An antipope, known as Clement III, 1080 (1084) to 1100; born at Parma about 1025; died at Cività Castellana, 8 Sept., 1100. This adversary of Pope Gregory VII and of his reform policies came from a noble family of Parma, which was related to the Margraves of Canossa. We first find him in history as a cleric and imperial chancellor for Italy. This office he received in the year 1057 from the Empress Agnes. He retained it until 1063. Guibert took part in the synod which was held by the newly elected pope, Nicholas II (1058-1061), at Sutri in January, 1059. But on the latter's death he contrived through his influence with the anti-reform party of the Upper Italian clergy and at the imperial court to bring about the election of the antipope, Cadalous of Parma (Honorius II), and became an opponent of Pope Alexander II. Owing to the active support of Duke Godfrey of Lorraine, of Archbishop Anno of Cologne, and especially of St. Peter Damian, the lawful pope was soon recognized even in Germany and by the Empress Agnes. Perhaps this was the reason of Guibert's dismissal in 1063 from the chancellorship. The following nine years give us no trace of him. He must have continued, however, in friendly relations with the German Court, and retained the favour of the Empress Agnes, for when, in the year 1072, the Archbishopric of Ravenna became vacant, Emperor Henry IV, on the recommendation of the empress, named him to this important archiepiscopal see. Pope Alexander II hesitated to confirm this choice, but was prevailed upon by Cardinal Hildebrand to sanction it. Guibert thereupon took the oath of allegiance to the Holy Father and to his successors, and was consecrated Archbishop of Ravenna (1073).

Alexander II died shortly afterwards, and was succeeded by Hildebrand, who assumed his holy office on 29 April, 1073, under the name of Gregory VII. Guibert participated in the first Lenten synod of the new pope, which was held in Rome (March, 1074), and at which important laws were passed against simony and the incontinence of the clergy. But it was not long before he joined the party in opposition to the great pontiff, with whom he had quarrelled about the city of Imola. The accusation was made against him that he had entered into an alliance with Cencius and Cardinal Hugo Candidus, the antagonists of Gregory VII in Rome. He absented himself from the Lenten Synod of 1075, although he was bound by oath to obey the summons to attend it. By his absence he made manifest his opposition to Gregory VII, who now suspended him for his refusal to attend the synod. It was in this same year that Emperor Henry IV began his open war on Gregory. At the synod of the German bishops at Worms (January, 1076), a resolution was adopted deposing Gregory, and in this decision the simoniacal bishops of Lombardy joined. Among these must have been Guibert, for he shared in the sentence of excommunication and interdiction which Gregory VII pronounced against the guilty bishops of Upper Italy at the Lenten Synod of 1076.

In April of the same year a synod was held at Pavia by a number of Lombard bishops and abbots, presided over by Guibert. As these did not hesitate to proclaim the excommunication of the pope, Gregory found himself compelled to resort to still stronger measures with regard to Guibert. At the Lenten Synod of February, 1078, he excommunicated Guibert by name, and with him Archbishop Tebaldo of Milan. In March, 1080, he renewed his decree of anathema against Henry IV, and gave his recognition to Rudolph of Swabia as ruler of Germany, whereupon Henry summoned such partisans as he had among the German and Lombard bishops to a meeting at Brixen (June, 1080). This meeting drew up a new decree purporting to depose the sovereign pontiff, which Henry himself also signed, and then proceeded to elect the Archbishop of Ravenna antipope. Henry at once recognized him as pope, swearing that he would lead him to Rome, and there receive from his hands the imperial crown. Guibert put on papal garments and proceeded with great pomp to Ravenna. At the Lenten Synod of 1081 Gregory VII reiterated against Henry and his followers his decree of excommunication. The antipope failed to secure recognition outside of Henry's dominions; he was in fact but a tool in the hands of the latter, and quite devoid of personal initiative. On 21 March, 1084, Henry IV succeeded after many fruitless attempts in gaining possession of the greater part of Rome. Gregory VII found himself besieged in the Castle of Sant' Angelo, while, on 24 March, Guibert was enthroned as pope in the church of St. John Lateran as Clement III. On 31 March Guibert crowned Henry IV emperor at St. Peter's. However, when the news was brought that Robert Guiscard was hastening to the aid of Gregory, Henry with his antipope left Rome to take up the fight in Tuscany against the troops of the Margravine Matilda. Gregory, escorted by Robert Guiscard, repaired to Salerno, where he renewed his excommunication of Henry and Guibert. This was at the close of the year 1084.

The German episcopate stood divided. While bishops loyal to Gregory held a synod in Quedlinburg, at which they denounced and condemned the antipope, those who supported Henry approved at Mainz the deposition of Gregory and the elevation of Guibert (1085). This conflict continued even after the death of the great Gregory (25 May, 1085), during the entire reigns of whose successors, Victor III, Urban II, and Paschal II, Guibert figured as the antipope of Henry and his party. Victor III, who was elected after a prolonged vacancy caused by the critical position of the Church in Rome, was compelled, eight days after his coronation in St. Peter's (3 May, 1087), to fly from Rome before the partisans of Guibert. The latter were in turn assailed by the troops of Countess Matilda, and entrenched themselves in the Pantheon. The succeeding pope, Urban II (1088-1099), was at one time master of Rome, but he was afterwards driven from the city by the adherents of Guibert, and sought refuge in Lower Italy and in France. In June, 1089, at a pseudo-synod held in Rome, the antipope declared invalid the decree of excommunication launched against Henry, and various charges were made against the supporters of the legitimate pope. Still, the years which followed brought to Urban ever-increasing prestige, while Henry IV's power and influence were more and more on the wane. The greater part of the city of Rome was captured by an army of crusaders under Count Hugh of Vermandois, brother of the King of France. The party of Guibert retained only the castle of Sant' Angelo, and even this in 1098 fell into the hands of the papal champion. Guibert's influence, after Henry IV's withdrawal from Italy, was virtually confined to Ravenna and a few other districts of Northern Italy. He repaired to Albano after the accession of Paschal II (1099-1118), hoping again to become master of Rome, but he was compelled to withdraw. He reached Cività Castellana, where he died on 8 September, 1100. His followers, it is true, elected another antipope, Bishop Theodorus of S. Rufina, who, however, never held any real power. (Compare also the articles GREGORY VII; VICTOR III; URBAN II; and PASCHAL II.)

Libelli de lite Imperatorum et Pontificum saec. XI et XII conscripti in Mon. Germ, hist. (3 vols., Hanover, 1890-1897); JAFFÉ, Regesta Romanorum Pontif., 2nd ed., I, 649-55; KÖHNCKE, Wibert von Ravenna (Leipzig, 1888); HEFELE, Konziliengesch., 2nd ed., V, 20 sqq.; HERGENRÖTHER AND KIRSCH, Kirchengesch., 4th ed., II, 346 sqq.: cf. also the bibliography given under the articles mentioned above.

J.P. KIRSCH