Pope Pius XI, born Ambrogio Damiano Achille Ratti;(31 May 1857 – 10 February 1939), reigned as Pope from 6 February 1922 to his death in 1939.
- Acerba animi (On the Persecution of the Church in Mexico) – September 29, 1932Ereader Files: English [ MOBI– EPUB ]
- Ad Catholici Sacerdotii (On the Catholic Priesthood) – December 20, 1935Ereader Files: English [ MOBI– EPUB ]
- Ad Salutem (On St. Augustine) – April 30, 1930Ereader Files: English [ MOBI– EPUB ]
- Apostolicorum in Missionibus (Decree naming St. Therese co-patron along with St. Francis Xavier of all foreign missions) – December 14, 1927Ereader Files: Latin [ MOBI– EPUB ]
- Caritate Christi Compulsi (On the Sacred Heart) – May 3, 1932Ereader Files: English [ MOBI– EPUB ]
- Casti Connubii (On Christian Marriage) – December 31, 1930Ereader Files: English [ MOBI– EPUB ]
- Dilectissima Nobis (On the Persecution of the Church in Spain) – June 3, 1933Ereader Files: English [ MOBI– EPUB ]
- Divini Illius Magistri (On Christian Education) – December 31, 1929Ereader Files: English [ MOBI– EPUB ]
- Divini Redemptoris (On Atheistic Communism) – March 19, 1937Ereader Files: English [ MOBI– EPUB ]
- Ecclesiam Dei (On St. Jehosophat) – November 12, 1923Ereader Files: English [ MOBI– EPUB ]
- Ingravescentibus Malis (On the Rosary) – September 29, 1937Ereader Files: English [ MOBI– EPUB ]
- Iniquis Afflictisque (On the Persecution of the Church in Mexico) – November 18, 1926Ereader Files: English [ MOBI– EPUB ]
- Lux Veritatis (On the Council of Ephesus) – December 25, 1931Ereader Files: English [ MOBI– EPUB ]
- Maximam Gravissimamque (On French Diocesan Association) – January 18, 1924Ereader Files: English [ MOBI– EPUB ]
- Mens Nostra (Promotion of the Spiritual Exercises) – December 20, 1929Ereader Files: English [ MOBI– EPUB ]
- Miserentissimus Redemptor (Reparation to the Sacred Heart) – May 8, 1928Ereader Files: English [ MOBI– EPUB ]
- Mit Brennender Sorge (On the Church and the German Reich) – March 14, 1937Ereader Files: English [ MOBI– EPUB ]
- Mortalium Animos (On Religious Unity) – January 6, 1928Ereader Files: English [ MOBI– EPUB ]
- Non Abbiamo Bisogno (Catholic Action in Italy) – June 29, 1931Ereader Files: English [ MOBI– EPUB ]
- Nos Es Muy Conocida (On the Religious Situation in Mexico) – March 28, 1937Ereader Files: English [ MOBI– EPUB ]
- Nova Impendet (On the Economic Crisis) – October 2, 1931Ereader Files: English [ MOBI– EPUB ]
- Quadragesimo Anno (Reconstruction of the Social Order) – May 15, 1931Ereader Files: English [ MOBI– EPUB ]
- Quas Primas (Introducing the Feast of Christ the King) – December 11, 1925Ereader Files: English [ MOBI– EPUB ]
- Quinquagesimo Ante (On his Sacred Jubilee) – December 23, 1929Ereader Files: English [ MOBI– EPUB ]
- Rerum condicio (Apostolic Constitution reforming the Rule of the Third Order Regular) – October 4, 1927Ereader Files: English [ MOBI– EPUB– ] Latin [ MOBI– EPUB ]
- Rerum Ecclesiae (On Catholic Missions) – February 8, 1926Ereader Files: English [ MOBI– EPUB ]
- Rerum Omnium Perturbationem (St. Francis De Salles) – January 26, 1923Ereader Files: English [ MOBI– EPUB ]
- Rerum Orientalium (On the Promotion of Oriental Studies) – September 8, 1928Ereader Files: English [ MOBI– EPUB ]
- Rite Expiatis (On St. Francis of Assisi) – April 13, 1926Ereader Files: English [ MOBI– EPUB ]
- Studiorum Ducem (On St. Thomas Aquinas) – June 29, 1923Ereader Files: English [ MOBI– EPUB ]
- Ubi Arcano Dei Consilio (On the Peace of Christ in HIs Kingdom) – December 23, 1922Ereader Files: English [ MOBI– EPUB ]
- Vigilanti Cura (On Motion Pictures) – June 29, 1936Ereader Files: English [ MOBI– EPUB ]