William Filby was an English Roman Catholic priest born in Oxfordshire between 1557 and 1560. After studying at Lincoln College, Oxford, he entered the seminary in Reims, where he was ordained in 1581. Shortly after his ordination, he traveled to England to participate in the Catholic mission. His involvement in the religious landscape of the era led to his arrest in July 1582 alongside Edmund Campion. Following his imprisonment, he was sentenced to death and executed at Tyburn on 30 May 1582.