St. Teresa of Ávila was a Spanish nun, born in 1515 on her mother's family farm in Gotarrendura, near Ávila. She initiated her career as a religious in 1535 by running away to the Carmelite convent of the Encarnacíon in Ávila, against her father's will. She donned the habit the following year and professed as a nun the year after. She lived for more than twenty years in the comfortable, large convent. The rules were relaxed, and women who entered could, even after taking the veil, retain their aristocratic titles, bring servants to accompany them, and entertain visitors, often handsome young men, in the convent parlor.

1560 was an annus mirabilis for Teresa. She experienced some of her most dramatic mystical visions, including a vision of the risen Christ and what is known as the transverberation , the piercing of her heart by an angel, the mystical event for which she is most famous and Bernini represented in The Ecstasy of Saint Teresa. She also had a vivid experience of being cast into Hell. This was also the year she formed her resolve, in response to a divine prompting, to reform the Carmelite order to its original purity of enclosure and poverty. The contemporary Order had been mitigated in its severity from the original Rule, received, as tradition holds, from the Desert Fathers of Mount Carmel centuries before in the Holy Land. She became determined to provide an atmosphere in which all distractions from the pure contemplation of God would be removed, and nuns could spend their lives in perfect, solitary recollection, alone with God.

Teresa received the requisite permission from Pope Pius IV to proceed with the foundation of the first convent of her Reform, San José de Ávila, and her life changed dramatically and permanently. For the next twenty years, she traveled widely and tirelessly, personally founding convents of the Reform in Ávila, Medina del Campo, Malagón, Valladolid, Pastrana, Salamanca, Alba de Tormes, Segovia, Beas, Seville, Caravaca, Villanueva, Palencia, Villanueva de la Jara, Burgos, and overseeing the foundation of a monastery for reformed friars in Duruelo. Death interrupted her journeys, at Alba de Tormes, in 1582.

Not only a tireless reformer, Teresa wrote equally tirelessly, producing first her Life, then documenting her reformed Foundations. Her classic writings on theology, still in print four hundred years later, describe the nature of contemplative prayer. She envisioned this as a lifelong, dynamic process. In her books Interior Castle and The Way of PerfectionI she identifies seven successive metaphorical stages of the soul's progression, through distinct "sorrows" and "blessings," towards ultimate union with God. Teresa was named Doctor of Theology by the Church in 1970, one of only two women so honored, together with St. Catherine of Siena.