French postage stamp commemorating Saint Teresa of Avila, also called Saint Teresa of Jesus, (28 March 1515 – 4 October 1582), Spanish mystic, Roman Catholic saint, Carmelite nun and author during the Counter Reformation, and theologian of contemplative life through mental prayer. She was a reformer in the Carmelite Order of her time and the movement she initiated, later joined by Saint John of the Cross, eventually led to the establishment of the Discalced Carmelites, though neither she nor John were alive when the two orders separated.