Teresa de Cepeda y Alumada was born into a noble family in Castille.
At the age of 20 she entered the Carmel monastery of the Incarnation of Avila.
She took the name Teresa of Jesus and discovered in prayer, a place of friendship and intimacy with Christ.
In 1555, contemplating Christ on the cross and reading the Confessions of St. Augustine, she desired to live her Carmelite vocation to the full. She realized that the religious practices of the Order had deteriorated and thus wanted to reform it, to get it back to the original Rule, in order to more closely follow Christ in prayer, poverty and the simplicity of a fraternal life.
She was a woman of many mystical experiences and dedicated much of her time to writing.
After founding many monasteries in Spain, she persuaded St. John of the Cross, a mystic himself, to initiate a similar reform. Thus, in 1567, the two of them began of work of founding the Discalced Carmelites.
Teresa was beatified in 1614 by Pope Paul V, and canonized by Gregory XV, on March 12, 1622. Pope Paul VI proclaimed her Doctor of the Church in 1970.
The Church celebrates the feast of Saint Teresa on October 15.