The Church marks a remarkable jubilee in 2026: the centenary of World Mission Sunday. Across that century, nine popes have helped the faithful understand this annual observance through their teaching, witness and appeals for prayer and generosity.
Multiple volumes would be needed to present the richness of that papal teaching. What follows is a brief overview of pivotal missionary documents and emphases from each pontificate.
Pope Pius XI (1922-1939). Pius XI established World Mission Sunday in 1926 in response to a proposal from the Society for the Propagation of the Faith. Celebrated throughout the Catholic world, the day was intended to unite the faithful in prayer, missionary awareness and material support for the Church's mission.
That same year, Pius XI issued Rerum Ecclesiae, an encyclical often described as a charter for modern Catholic mission. He insisted that missionary activity must foster strong local Churches rather than indefinite dependence on missionaries from abroad. He called for the careful formation of local priests, religious and catechists, stressing that local clergy shared fully in the same priesthood and apostolate as foreign missionaries. These priorities remain visible wherever the Church builds seminaries, forms catechists and prepares local leaders to assume responsibility for evangelization.
Pope Pius XII (1939-1958). Pius XII led the Church through World War II and the first decades of postwar reconstruction and decolonization. Against that turbulent background, he issued two major missionary encyclicals: Evangelii Praecones in 1951 and Fidei Donum in 1957.
Evangelii Praecones, published for the 25th anniversary of Rerum Ecclesiae, noted the growth of local clergy, religious and bishops despite the disruption of war. It encouraged missionaries to recognize and build upon what was good in local cultures. Fidei Donum focused especially on Africa and called dioceses with more clergy to share priests with Churches facing severe shortages. The goal was the firm and lasting establishment of local Churches.
Pope St. John XXIII (1958-1963). During a pontificate of less than five years, John XXIII convened the Second Vatican Council and issued eight encyclicals addressing subjects that included peace, social justice, human dignity and Christian unity.
Although he presided only over the Council's first session in 1962, the renewal he initiated profoundly shaped the Church's understanding of mission.
His missionary encyclical Princeps Pastorum (1959) emphasized the formation of local clergy, the maturation of young Churches, respect for local cultures and the active participation of laypeople. Mater et Magistra (1961) addressed economic inequality and the relationship between wealthier and developing nations, while Pacem in Terris (1963) placed human rights, peace and international cooperation at the center of the Church's engagement with the modern world.
Pope St. Paul VI (1963-1978). Paul VI guided the final three sessions of the Second Vatican Council and brought it to completion. Several conciliar documents contributed to a profound renewal of missionary theology and practice, especially Lumen Gentium, Gaudium et Spes, Unitatis Redintegratio, Ad Gentes, Apostolicam Actuositatem and Nostra Aetate.
Paul VI's greatest missionary contribution was his 1975 apostolic exhortation Evangelii Nuntiandi. He affirmed that "the task of evangelizing all people constitutes the essential mission of the Church" and that evangelizing is "the grace and vocation proper to the Church, her deepest identity" (No. 14). To evangelize, he explained, means "bringing the Good News into all strata of humanity, and through its influence transforming humanity from within" (No. 18).
Paul VI's World Mission Sunday messages repeatedly emphasized unity, peace, Christian witness, joy, hope and the proclamation of the Gospel in modern society. He also became the first pope of the modern era to make international apostolic journeys, embodying in a new way the universal scope of the Petrine ministry.
Pope John Paul I (1978). John Paul I served for only 33 days and did not issue a World Mission Sunday message. By taking the names of his two immediate predecessors, he signaled his intention to continue the renewal of the Second Vatican Council. His warmth, humility and joy earned him the affectionate title "the smiling pope."
Pope St. John Paul II (1978-2005). John Paul II served for more than 26 years, one of the longest pontificates in the Church's history. The first non-Italian pope in 455 years, he carried the Gospel around the world through an unprecedented program of apostolic journeys.
His witness helped inspire resistance to communist rule in his native Poland and elsewhere in Central and Eastern Europe. His global pastoral presence also made the missionary character of the papacy visible to millions.
In more than two dozen World Mission Sunday messages, John Paul II emphasized that evangelization is a fundamental responsibility of all Christians, expressed through prayer, personal witness, respect for human dignity and material support. His 1990 encyclical Redemptoris Missio offered a comprehensive account of the Church's missionary mandate. "Mission is an issue of faith," he wrote, "an accurate indicator of our faith in Christ and his love for us" (No. 11).
Pope Benedict XVI (2005-2013). Benedict XVI issued seven World Mission Sunday messages, showing the inseparable relationship among Christian charity, Gospel proclamation, ecclesial communion and lay participation. Although he did not publish an encyclical devoted specifically to missionary activity, his teaching consistently presented faith as a gift that must be shared and Christian love as an essential form of witness.
Pope Francis (2013-2025). The first pope from the Americas and the first Jesuit pope, Francis issued 13 World Mission Sunday messages, from 2013 through 2025. Their themes included mercy, youth, hope, missionary conversion and the call to be disciples whose hearts burn for the Gospel and whose feet are ready to carry it to others.
His 2013 apostolic exhortation Evangelii Gaudium supplied the programmatic vision for his pontificate. "Missionary outreach is paradigmatic for all the Church's activity," he wrote (No. 15), urging the faithful to be "permanently in a state of mission" (No. 25). He called every baptized person to recognize his or her identity as a missionary disciple.
Pope Leo XIV (2025- ). Pope Leo's first World Mission Sunday message marks the centenary of the observance. For 2026, he chose the theme "One in Christ, united in mission." Drawing upon his experience as a missionary priest and bishop in Peru, he teaches that union with Christ lies at the heart of mission, that no baptized person is exempt from it and that reconciled communities are needed to radiate Christ's love in a divided world.
A missionary dimension is also present in Pope Leo's first encyclical, Magnifica Humanitas, on safeguarding the human person in the age of artificial intelligence. Its teaching on human dignity, solidarity, the common good and the inclusion of the most vulnerable offers important guidance for the Church's witness amid rapid technological change.
Conclusion. This brief survey can serve only as an invitation to explore more deeply the Church's missionary teaching over the past century. Together, these papal voices remind us that mission is not a specialized concern for a few, but a responsibility shared by the entire people of God.
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** The author was a missionary in Asia (Philippines and Bangladesh) for over five decades. His recent publications are: Walking with Pope Francis (Orbis Books) and three short, meditative books: Living in Joyful Hope, Exploring Vatican II Treasures, and A Joyful Journey with Pope Francis (www.faithalivebooks.com).
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