Grandson of King Radbon of the Frisians. Educated by the priests at Utrecht. Priest, known for his learning and personal piety. Catechist and instructor to converts. Bishop of Utrecht in 825. Frederick worked to reform his clergy, regularize Church practice in his diocese, and opposed incestuous marriages, especially among the nobility. He dispatched a group of missionaries under the leadership to Saint Odulphus to evangelize the pagans to the north of Utrecht, and worked with them around Walcheren. He composed a prayer to the Blessed Trinity that was used for ages in the Netherlands. The memory of his live and sanctity were preserved in a poem by his contemporary Saint Rabanus Maurus.
Frederick became involved in the royal politics of his day, and was especially involved in the domestic problems of Emperor Louis the Debonair, Empress Judith, and their sons. Frederick openly chastised Judith for her immoral and adulterous lifestyle, which has led many writers to conclude that Judith hired the men who murdered Frederick. However, it is more likely that they were pagans from Walcheren, many of whom were violently opposed to the Christian missionaries, and who martyred him for his work.
stabbed to death during Mass on 18 July 838