Pope Pius X issued 17 papal encyclicals during his reign as Pope:
No. Title (Latin) Title (English translation) Subject Date Text1. E supremi "On high" On the Restoration of All things in Christ 4 October 1903 2. Ad diem illum laetissimum "On that most happy day" On the Immaculate Conception 2 February 1904 3. Iucunda sane On Pope Gregory the Great 12 March 1904 4. Acerbo nimis "At This Extremely Harsh (Time)" On Teaching Christian Doctrine 15 April 1905 5. Il fermo proposito On Catholic Action in Italy 11 June 1905 6. Vehementer Nos "We with vehemence" On the French Law of Separation 11 February 1906 7. Tribus circiter "Circumscribed tribes" On the Mariavites: Mystic Priests of Poland 5 April 1906 8. Pieni l'animo On the Clergy in Italy 28 July 1906 9. Gravissimo officii munere On French Associations of Worship 10 August 1906 10. Une fois encore On the Separation of Church and State 6 January 1907 11. Pascendi dominici gregis "The Feedings of the Flock of the Lord" On the Doctrine of the Modernists 8 September 1907 12. Communium rerum "Of Common Things" On St. Anselm of Aosta 21 April 1909 13. Editae saepe On St. Charles Borromeo 26 May 1910 14. Notre charge apostolique “Our Apostolic Mandate” On socialist doctrines of the Sillon movement 15 August 1910 15. Iamdudum "Long since" On the Law of Separation in Portugal 24 May 1911 16. Lacrimabili statu "In a tearful state" On the Indians of South America 7 June 1912 17. Singulari quadam On Labour Organisations 24 September 1912