Pope Pius XI (259º): Biography, Pontificate & Legacy

Who Was Pope Pius XI?

Among the 267 popes, Pius XI is number 259, remembered for the years 6 February 1922–10 February 1939 in the modern papacy. Subject of the Kingdom of Lombardy–Venetia, later becoming an Italian citizen. Use the sections below to move from a one-line summary of Pius XI to a usable historical and spiritual picture.

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.

Historical Context

Pius XI (#undefined) served while industry, world wars, the loss of the Papal States, and Vatican councils remade how Rome speaks to a mass society. 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

Acts associated with Pius XI (#259, 6 February 1922–10 February 1939) still draw historians and Catholics who want more than a one-line summary. His reign remains a link in the succession now counted at 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. Set against the modern papacy, Pius XI's choices show both the limits of any one pontiff and the continuity of the office he held.

Why Catholics Study This Pope Today

Place Pius XI on your mental map: 259º successor of Peter, reigning 6 February 1922–10 February 1939, formed by the modern papacy. Start with the concrete record: Instituted the feast of Christ the King. Signed the Lateran Treaty with Italy (1929), establishing Vatican City as a sovereign state. Where bulls, conciliar acts, or encyclicals survive from this reign, they repay readers who want primary sources rather than summaries alone. Compare Pius XI with the biographies of his predecessor and successor linked below to see reform, rupture, or quiet continuity.

Place in the Line of Succession

Pius XI followed Pope Benedict XV (258º, 3 September 1914–22 January 1922) after a transition shaped by the politics and piety of their shared century. He was followed by Pope Ven. Pius XII (260º, 2 March 1939–9 October 1958), whose biography continues the chain on Guide Catholic. For the full chronological map, see our complete list of all 267 popes — then read neighboring biographies for contrast, not only continuity.