St. Bruno Of Querfur (Brun, Bruns) (c. 975-1009), German missionary bishop and martyr, belonged to the family of the lords of Querfurt in Saxony. He was educated at the famous cathedral school at Magdeburg, and at the age of twenty was attached to the clerical household of the emperor Otto III. In 996 he accompanied the emperor to Rome, and there gave up his post and entered the monastery of SS. Alexius and Bonifacius on the Aventine, taking "in religion" the name of Bonifacius. When the news reached Rome of the martyrdom of Adalbert, bishop of Prague (997), Bruno determined to take his place, and in 1004, after being consecrated by the pope as archbishop of the eastern heathen, he set out for Germany to seek aid of the emperor Henry II. The emperor, however, being at war with Boleslaus of Poland, opposed his enterprise, and he went first to the court of St Stephen of Hungary, and, finding but slight encouragement there, to that of the grand prince Vladimir at Kiev. He made no effort to win over Vladimir to the Roman obedience, but devoted himself to the conversion of the pagan Pechenegs who inhabited the country between the Don and the Danube. In this he was so far successful that they made peace with the grand prince and were for a while nominally Christians. In 1008 Bruno went to the court of Boleslaus, and, after a vain effort to persuade the emperor to end the war between Germans and Poles, determined at all hazards to proceed with his mission to the Prussians. With eighteen companions he set out; but on the borders of the Russian (Lithuanian) country he and all his company were massacred by the heathens (February 14, 1009).

During his stay in Hungary (1004) Bruno wrote a life of St Adalbert, the best of the three extant biographies of the saint (in Pertz, Mon. Germ. Hist. Scriptores, iv. pp. 577, 596-612), described by A. Potthast (Bibliotheca hist. med. aev.) as "in the highest degree attractive both in manner and matter."

A life of St Bruno was written by Dietmar, bishop of Merseburg (976-1019). This, with additions from the life of St Romuald, is published in the Bollandist Acta Sanctorum (June 19), vi. 1, pp. 223-225. See further U. Chevalier, Répertoire des sources historiques, Bio-Bibliographie (Paris, 1904), s.v. "Brunon de Querfurt."