San Juan de la Cruz, also known as Saint John of the Cross, was a Spanish mystic and poet born in 1542. He is best known for his role in the Carmelite Order and for his deep spiritual writings, which explore the soul's journey toward God. His works, such as "Dark Night of the Soul," emphasize the importance of inner purification and union with the divine. He was canonized as a saint in 1726 and is recognized as a Doctor of the Church for his contributions to Christian mysticism. San Juan de la Cruz is celebrated on December 14, and his teachings continue to inspire many in their spiritual practices.