St. Augustine

Aurelius Augustinus, Augustine of Hippo (November 13, 354-August 28, 430) is a saint and the pre-eminent Doctor of the Church according to Roman Catholicism; he was the eldest son of Saint Monica. In the Eastern Orthodox Church, which does not accept all of his teachings, he is usually called "Blessed Augustine." Many Protestants consider him to be a spiritual ancestor of Protestantism, in the sense that Protestantism's founder Martin Luther was deeply influenced by him (Luther was trained as an Augustinian monk).