Bruno of Querfurt, O.S.B. Cam., also known as Brun, was a Christian missionary, bishop, Camaldolese monk and martyr. He was active in the eastern regions of the Holy Roman Empire and became one of the leading figures in the early Christian missions to the peoples of northeastern Europe. Bruno was killed in Prussia, near the frontier of Kyivan Rus' and Lithuania, while attempting to convert the Old Prussians to Christianity. He is venerated as the "Second Apostle of the Prussians".