Thomas Illyricus (1484/5–1528/9) was a Dalmatian Franciscan theologian, hermit, pilgrim and itinerant preacher who spent most of his life in southern France. He is known for the purported discovery of the venerated image of Our Lady of Arcachon. He gained a substantial following for his prophetic preaching and advocacy of church reform. He later wrote two early critiques of Martin Luther.