The Mystical City of God was written in the 17th century by the Franciscan nun, Mary of Jesus of Ágreda.

The book tells the life of he Virgin Mary and the divine plan for creation and the salvation of souls. According to María de Ágreda, the book was largely dictated to her by the Virgin Mary herself. The book alternates between describing the Trinity, the Virgin Mary's life, and giving spiritual guidance to the author, which also spiritually benefit the reader as well. The book describes the virtues, and how the reader should conduct his or her life using the Virgin Mary as a model for sanctity.

This work bears the Imprimatur of several Popes and Bishops. However various misinterpretations of her writings led to it being temporarily placed on the Church's Banned Book List (Index Librorum Prohibitorum) in August 1681. But with the order of Blessed Innocent XI, the decree of condemnation was removed three months later, after it was shown that a faulty French translation was at the basis for the censure. The book was subsequently criticized by Jansenists and Gallicans in the 18th century, while the Church continued to defend its orthodoxy.

In 1673, María de Ágreda was declared venerable soon after her death.