St. Teresa of Ávila was a Spanish mystic and reformer born on March 28, 1515. She is best known for her role in the Carmelite Order, where she established the Discalced Carmelites, a reformed branch emphasizing a more contemplative and austere lifestyle. Her writings on prayer and spirituality, including "The Interior Castle," have had a lasting impact on Christian mysticism. In 1970, St. Teresa became the first woman to be declared a Doctor of the Church, recognizing her significant contributions to theology and spirituality. She was canonized in 1614 and is celebrated on October 15 each year, reflecting her enduring influence in the Catholic faith.