History’s first American pope, Leo XIV, will formally begin his papacy on Sunday in a ceremony at St. Peter’s Basilica filled with deep Catholic tradition, global symbolism, and high-level diplomatic presence. Nearly 150 official delegations are expected, with an estimated 250,000 attendees crowding into St. Peter’s Square for the inaugural Mass.
Leo, a 69-year-old Augustinian missionary born in Chicago, will begin the day with a traditional popemobile tour through the piazza, his first public interaction with pilgrims and dignitaries since his election. Though considered more reserved than his predecessor, Pope Francis, Leo is expected to connect with the crowd in the same spirit of accessibility.
Following the tour, Leo will pray at the tomb of St. Peter before proceeding to the altar for the formal Mass. Key elements of the ceremony include receiving the pallium and the fisherman’s ring—symbols of pastoral responsibility and apostolic authority. These moments signal the spiritual and global duties Leo now carries as head of the Catholic Church.
U.S. Vice President JD Vance and Secretary of State Marco Rubio will represent the American delegation, given Leo’s dual U.S.-Peruvian citizenship. Peruvian President Dina Boluarte and Ukrainian President Volodymyr Zelenskyy are among several heads of state in attendance.
Leo is expected to address modern global challenges, particularly his stated priorities of seeking peace in global conflict zones and grappling with the rise of artificial intelligence. His focus echoes that of Pope Leo XIII, who confronted similar upheaval during the industrial age.
Security is heightened following Pope Francis’ funeral in April. Giant screens and facilities have been deployed to accommodate the overflow crowds, underscoring the historical weight of this papal installation and the attention surrounding Leo XIV’s early leadership.
