I. Or Aldebert, a Frankish bishop and missionary to the German pagans before the middle of the 8th century. He was accused of heresy by St. Boniface, who charged him among other things with collecting his own hair and nails as relics. He was condemned by a synod held in 745, and died in prison. His disciples were styled Adalbertines, or Aldebertines.

II. Saint, of Prague, " the apostle of the Prussians," died in 997. He was educated by the celebrated Otherich at Magdeburg. In 983 he was chosen bishop of Prague. Discouraged at his failure to convert the Bohemians, he repaired to the monastery of St. Alexius at Rome. In 993 he was recalled to his bishopric, but after two years became again disgusted and left. In 995 he baptized the future St. Stephen and first king of the Hungarians at Gran. He subsequently went to Poland, and thence to Prussia, to concert the heathen, by whom he was murdered.

III. Archbishop of Bremen and Hamburg, died at Goslar, March 17, 1072. He received his office in 1043 from Henry III., whom in 1046 he accompanied to Rome. There he was a candidate for the papal throne, and barely failed in the election. Pope Leo IX., in whose behalf he had spoken in the synod at Mayence in 1049, made him in 1050 his legate in the north. During the minority of the emperor Henry IV. he usurped, together with Archbishop Hanno of Cologne, the administration of the empire. He became so obnoxious to the German princes, that in 1066 they forcibly separated him from the emperor; but in 10G9 he regained his power, and kept it till his death.