Bruno was born of the Saxon nobility, kin to Emperor Otto III, and was educated in the cathedral school of Magdeburg. At the imperial court he met Adalbert of Prague and was caught by the missionary impulse that had just sent Adalbert to his death in 997. After Otto III's own death in 1002, Bruno became a Camaldolese hermit under Romuald at Pereum near Ravenna, then was consecrated archbishop ad gentes (to the heathen) by Pope John XVIII in 1004.
He preached in Hungary, Kievan Rus' (where he met Vladimir), and finally among the Prussians and the Yotvingians on the eastern Baltic frontier. In 1009, near the modern Polish-Lithuanian border, he and his companions were attacked and beheaded for refusing to leave. His Life of the Five Brothers — the five Polish companions of Adalbert who were martyred in 1003 — and his Life of St. Adalbert are foundational documents of Slavic Christianity.