Saint Bruno of Querfurt was a 10th-century missionary and bishop known for his efforts to spread Christianity in Eastern Europe. Born around 974 in Germany, he became a monk and later dedicated his life to missionary work, particularly among the Slavs and Hungarians. His commitment to evangelization led him to travel extensively, establishing churches and converting many to Christianity. Bruno was eventually martyred in 1009 while preaching in Prussia. His death marked him as a significant figure in the history of Christian missions in the region. He was canonized as a saint, and his feast day is celebrated on June 15.