Papal inauguration of Pope Leo XIV

On 18 May 2025, Pope Leo XIV celebrated the inauguration Mass of his pontificate, formally known as the Mass for the Beginning of the Petrine Ministry of the Bishop of Rome. The event was attended by some 200,000 people, including dozens of world leaders and 150 formal delegations. While Leo became the Roman pontiff at the moment of his acceptance in the Sistine Chapel upon being elected in the 2025 papal conclave, the inauguration celebration marked the formal beginning of his ministry as the bishop of Rome. The Mass included the bestowal of the pallium and Ring of the Fisherman, and was followed by meetings with various delegations and world leaders.

Prior to the ceremony, Leo toured St. Peter's Square in the popemobile for the first time, where attendees shouted Viva il Papa! (Long live the Pope), and "USA, USA!" with at least one person chanting "White Sox!", referencing his country of birth and favorite baseball team. Others waved Peruvian or American flags for the countries that claim him as a citizen.

The liturgy formally began at 10 a.m. at Saint Peter's tomb underneath the baldachin of the high altar of St. Peter's basilica. Surrounded by the patriarchs of the Eastern Catholic Churches, Leo incensed the tomb while the choir sang Tu es Petrus, a motet by Giovanni Pierluigi da Palestrina. Ascending from the grottoes, Leo was joined in procession to the square by two deacons holding the Ring of the Fisherman and the papal pallium, as well as cardinals and bishops. The traditional Laudes Regiae chant was sung during the procession. Leo then conducted the asperges rite, typical on Sundays of Eastertide.

The first reading, from Acts 4:8-12, was proclaimed in Spanish, referencing Leo's work in the Diocese of Chiclayo. Psalm 118 was sung in Italian, for his new diocese; the second reading, from 1 Peter 5:1-5, 10-11, was proclaimed in English by a faculty member from the Pontifical North American College, referencing Leo's native tongue. The Gospel, John 21:15-19, was chanted in Latin by a deacon from the Diocese of Fort Wayne–South Bend, Indiana, then subsequently chanted in Greek.

Representing the cardinal deacons, Mario Zenari imposed the pallium on Leo's shoulders. Then, representing the cardinal priests, Fridolin Ambongo Besungu conferred a prayer of blessing on the pope. Finally, Luis Antonio Tagle, for cardinal bishops, then bestowed the Ring of the Fisherman upon the pontiff; Leo appeared visibly moved by the moment. Following the investment of the insignia, twelve delegates representing the Catholic Church from around the world, including clerics, vowed religious, a married couple, and young adults, were received by Leo. The homily delivered by Leo followed, where he spoke in Italian.

The prayers of the faithful were delivered in Arabic, Chinese, French, Polish, and Portuguese. Tu es pastor ovium was chanted during the offertory. Leo prayed the Roman Canon.

Before the conclusion of Mass, Leo offered some brief remarks, especially offering prayers for the conflicts in Gaza, Myanmar, and Ukraine. The Regina cæli was sung, followed by the final blessing.

Some 30 heads of state, 200 cardinals, and 750 bishops and priests were present. Throughout the ceremony, Leo used the papal ferula commonly used by Pope John Paul II.

Princess Charlene of Monaco, Queen Letizia of Spain, Queen Mathilde of Belgium, and Grand Duchess Maria Teresa of Luxembourg exercised the privilège du blanc extended to Catholic royalty by wearing white to the ceremony.

Leo began his sermon by thanking those who were present and remembering the emotions of the previous weeks following the death of Pope Francis and subsequent conclave. Recalling the two-fold aspects of ministry entrusted to Saint Peter, love and unity, Leo said he would approach the Church as a brother and servant and with "fear and trembling". Leo expressed a desire for unity and communion in the Church and in the world. He condemned exploitation of Earth's resources and marginalization of the poor. He referenced his papal motto, "in the one Christ, we are one", and exclaimed "Look to Christ! Come closer to him!"

After the ceremony, Leo entered St. Peter's basilica and met with 150 delegations in front of the St. Peter's baldachin. Among the delegations was his brother Louis, whom he embraced. After the inauguration, Leo met with Peruvian president Dina Boluarte and Ukrainian president Volodymyr Zelenskyy.

On Monday, 19 May, Leo met with US Vice President JD Vance and Secretary of State Marco Rubio. Vance appeared to give Leo a Chicago Bears jersey with the name "Pope Leo" and number "XIV". Leo also met with Gustavo Petro, president of Colombia; Bartholomew, the ecumenical patriarch of Constantinople; Gerardo Werthein, Minister of Foreign Affairs and Worship of Argentina; and representatives of other churches, ecclesiastical communities, and religions.

In the days following the inauguration, Leo took possession of the other major basilicas, with ceremonies held at the Basilica of Saint Paul Outside the Walls on 20 May, and at the Archbasilica of Saint John Lateran and the Basilica of Santa Maria Maggiore on 25 May, formally installing him as the Bishop of Rome.

Jewish, Muslim, Hindu, Buddhist, Sikh, Zoroastrian and Jainist leaders were present.