Pope Pius XI (259º): Biography, Pontificate & Legacy
Pontificate: 6 February 1922–10 February 1939
Pius XI was the 259th pope of the Catholic Church, reigning 6 February 1922–10 February 1939 during the modern papacy. Instituted the feast of Christ the King.
Who Was Pope Pius XI?
This biography of Pius XI (259º) covers background, major events, and legacy in the line of St. Peter. During the modern papacy, the Bishop of Rome exercised teaching, sanctifying, and governing authority for the universal Church.
Early Life & Background
Before election he was known as Ambrogio Damiano Achille Ratti. Born 31 May 1857 Desio, Kingdom of Lombardy–Venetia, Austrian Empire, he entered a world shaped by politics and piety very different from today's global Church. Subject of the Kingdom of Lombardy–Venetia, later becoming an Italian citizen.
Historical Context
Pius XI served during the modern papacy — a time of industrial revolution, world wars, the loss of the Papal States, Vatican I and II, and the Church's engagement with democracy, human rights, and mass media. Signed the Lateran Treaty with Italy (1929), establishing Vatican City as a sovereign state. Inaugurated the Vatican Radio(1931).
Pontificate & Key Events
The pontificate (6 February 1922–10 February 1939) centered on governance during the modern papacy. Refounded the Pontifical Academy of Sciences(1936). Opposed Nazism and Communism. During his pontificate, Catholic priest and physicist Georges Lemaître proposed what he called the "hypothesis of the primeval atom", now regarded as the first formulation of the Big Bang theory of the origin of the universe.
Papal Acts & Achievements
Pius XI left a distinct mark through decisions that historians still debate and Catholics still study. His reign contributed to the continuous apostolic succession now numbering 267 popes. Papal motto: Pax Christi in Regno Christi ("The Peace of Christ in the Kingdom of Christ").
Key Highlights
- 259th pope of the Catholic Church
- Pontificate: 6 February 1922–10 February 1939
- Shepherded the Church during the modern papacy
- Successor of St. Peter in the official Catholic list
Legacy in the Catholic Church
Pius XI remains pope 259º in the Annuario Pontificio. Read against the modern papacy, his pontificate shows how Providence works through imperfect ministers without abandoning the Barque of Peter.
Why Catholics Study This Pope Today
Studying Pius XI helps Catholics see how the Holy Spirit guided the Church through the modern papacy — with human weakness and grace intertwined. Primary sources from this pontificate — bulls, conciliar acts, or encyclicals — reward readers who want depth beyond summaries. Place this pope in context using our chronological list of all 267 popes and the biographies of his immediate predecessor and successor linked below.
Place in the Line of Succession
Pius XI followed Pope Benedict XV (258º) in the unbroken line of apostolic succession from St. Peter. Upon his death or resignation, he was succeeded by Pope Ven. Pius XII (260º), who continued the mission of shepherding the universal Church. Explore the full chronological chain in our complete list of all 267 popes, or read the biographies of neighboring pontiffs linked below.