Saint Frederick I was Bishop of Utrecht between 815 AD and 838 AD and is a Saint in both the Roman Catholic Church and the Eastern Orthodox Church.
Born around the year 780, Saint Frederick was the grandson of the Frisian King Radboud. As a young man he was educated at Utrecht by Bishop Ricfried and the other clergy there before being ordained a priest. Soon after his ordination he was sent to convert the remaining pagans in the northern areas of the diocese. It was on this journey that he breached at Walcheren alongside Saint Odulfus. When Bishop Ricfried died in 815 Saint Frederick was chosen to succeed him as Bishop.
As Bishop he became well known for his piety, knowledge and understanding, especially during the synod of Mainz in 829. Legend holds that Saint Frederick was murdered on July 18th, 838 after celebrating Mass. Affording to Bishop Otbert of Liege and William of Malmesbury, Saint Frederick was stabbed to death by two men hired by the Empress Judith due to his regular criticism of her lifestyle. A secondary theory put forward by Cesare Baronio and Jean Mabillon states that he was likely killed by pagans in Walcheren who were angered by his attempts to bring Christianity to the region.
He was very quickly canonized after his death and buried in Saint Salvator's Church in Utrecht. Today his feast day is celebrated on July 18th in the Catholic Church.