Bishop of Bamberg, b. about 1060; d. 30 June, 1139. He belonged to the noble, though not wealthy, family of Mistelbach in Swabia, not to the Counts of Andechs. He was ordained priest, but where he was educated is not known. While still young he joined the household of Duke Wladislaw of Poland; in 1090 he entered the service of Emperor Henry IV, and about 1101 was made chancellor. In 1102 the emperor appointed and invested him as Bishop of Bamberg. In the conflict of investitures (q.v.) he sided chiefly in political matters with Henry IV, although he avoided taking sides openly. He refused to be consecrated by a schismatic bishop. Through ambassadors he declared his loyalty to the Holy See. In 1105 he joined the party of Henry V, went to Rome, and there on 13 May, 1106, was consecrated bishop. He never became a partisan. In 1110-11 he accompanied Henry on his journey to Rome, but, like other noble characters, he disapproved of the disgraceful treatment of Pope Paschal. This is clear from the fact that he received the pallium from the pope on 15 April, 1111. When the war broke out again, he did not desert Henry V, and in consequence was suspended by the papal party at the Synod in Fritzlar in 1118. At the Congress of Würzburg in 1121 he strove hard for peace, which was concluded in 1122 at Worms. Meanwhile he had devoted himself entirely to his diocese and as bishop had led a model, simple, and even a poor life. He increased the possessions of the Church by new acquisitions, recovered alienated dependencies, completed the cathedral, improved the cathedral school, built castles and churches. In particular he favoured the monks, and founded over twenty monasteries in the Dioceses of Bamberg, Würzburg, Ratisbon, Passau, Eichstatt, Halberstadt and Aquileia. He reformed other monasteries. Thus he merited the name of "Father of the Monks".
His greatest service was his missionary work among the Pomeranians. In the Peace with Poland in 1120 the latter had engaged to adopt Christianity. Attempts to convert them through Polish priests and through an Italian Bishop, Bernard, proved futile. Duke Boleslaus III then appealed to Otto, and it is due to Otto that the undertaking partook of a German character. Through an understanding with the pope, who appointed him legate, the emperor and the princes, he started in May, 1124, and travelled through Prague, Breslau, Posen, and Gnesen in East Pomerania, was received by the duke with great respect, and won over the people through his quiet yet firm attitude, his magnificent appearance, generous donations, and gentle, inspiring sermons. He converted Pyritz, Kammin, Stettin, Julin, and in nine places established eleven churches; 22,165 persons were baptized. In 1125 he returned to Bamberg. As heathen customs began to assert themselves again, he once more journeyed to Pomerania through Magdeburg and Havelberg about the year 1128. In the Diet of Usedom he gained over through his inspiring discourses all the nobles of the land to Christendom. He then converted new communities, and led back those who had fallen away. Even after his return (in the same year) he was in constant communication with the Pomeranians and sent them priests from Bamberg. His wish to consecrate a bishop for Pomerania was not fulfilled as the Archbishops of Magdeburg and Gnesen claimed the metropolitan rights. Only in 1140 was his former companion Adalbert confirmed as Bishop of Julin. In 1188 the bishopric was removed to Hammin and made directly subject to the Holy See. In Bamberg he once more gave himself up to his duties as bishop and prince and performed them with great zeal. He kept out of all political turmoil. In the papal schism of 1130-31 he tried to remain neutral. The active, pious, clever bishop was greatly esteemed by the other princes and by Emperor Lothair. He was buried in the monastery of St. Michael in Bamberg. Bishop Embrice of Würzburg delivered the funeral oration and applied to Otto the words of Jeremias: "The Lord called thy name, a plentiful olive tree, fair, fruitful, and beautiful." On his mission journey he is reported to have worked many miracles. Many happened also at his tomb. In 1189 Otto was canonized by Clement III. His feast is kept on 30 September, partly also on 30 June; in Pomerania on 1 October.
LOOSHORN, Geschichte des Bistums Bamberg, II (Munich, 1888), 1-368; JURITSCH, Geschichte des Bischofs Otto I von Bamberg (gotha, 1889); WIESENER, Geschichte der christlichen Kirche in Pommern (Berlin, 1889); HAUCK, Kirchengeschichte Deutschlands, III (Leipzig, 1903), 571-87.