William Davies was a Welsh Catholic priest and missionary who lived during the Elizabethan era. Born in North Wales around 1555, he served as an underground schoolmaster on the Creuddyn Peninsula and operated a secret seminary at Penrhyn Hall. Following his ordination in 1585, he worked to support the Catholic faith through teaching and literature. After being apprehended at Holyhead in 1592, he was held in a dungeon at Beaumaris Castle until his execution in 1593.