She lived in a monastic setting for most of her life. At the age of 15, after the death of her mother, her father placed her into the care of Augustinian nuns. She joined the Carmelite order in 1535, where she led a life of more or less average religious progress, plagued by illness and spiritual dryness, until she experienced a life-changing vision of Christ.
From this point, her own spiritual exercises focused more and more on Christ’s passion, and turned towards ecstatic experience. Her contemplative life broadened out into an active life that embraced the reformation of the Carmelite order. From 1560 to her death, she worked to establish the Discalced (shoeless) Carmelites, in an effort to return the religious life to the strict observance of its earlier days. With assistance from a wealthy woman friend and patron, she founded the first monastery of the Discalced Carmelites in 1562; over the next 20 years, she would convince men — including St. John of the Cross — to join the reform effort as well, and extend the Discalced reforms to monks; weather persecutions from 1576 – 1579, and engage the support of Philip II of Spain to relieve them; record her spiritual practices and experiences in works that are now considered classics of the life of prayer and contemplation, in particular her Interior Castle.
Teresa was no ecumenist. She regarded Protestant theology as a wretched sectarian evil; her reforms were a response to that evil, one she hoped would mitigate it. Despite this, contemporary Protestants as well as Teresa’s Roman Catholic co-religionists embrace her accounts of the spiritual life, and recognize her as a significant figure in the history of their church.
Read More . . .
Christian Classics Ethereal Library has a biography, as well as online texts of Teresa’s works The Interior Castle, the Life of St. Teresa of Jesus, and The Way of Perfection.
Other Women’s Voices has a concise biography and extensive links to primary and secondary sources
A better view of The Ecstasy of St. Teresa in the Cornaro Chapel, with some good art historical commentary that reflects on the relationship of Baroque Art to the Counter-Reformation, is at SmartHistory.org