In a historic event on May 18, 2025, Pope Leo XIV led his inaugural Mass in St. Peter's Square, attended by approximately 150,000 people, including prominent world leaders such as Vice President JD Vance and President Volodymyr Zelensky of Ukraine. This event not only marked Leo's official start as the first American pope but also aimed to set a tone of inclusivity and unity.

During his homily, Leo emphasized the need to blend tradition with modernity, urging the church to confront today’s challenges while preserving its rich heritage. He expressed his intent to serve as a loving shepherd to the global Catholic community, advocating for peace in war-torn regions like Ukraine and Gaza, and calling for a united Church that values diversity.

The Mass featured heartfelt moments as Leo greeted attendees in an open-top popemobile and shared communion with the crowd. His message resonated with those present, emphasizing a "missionary spirit" that fosters dialogue among various faiths and communities. As the first pope from the Order of St. Augustine, Leo’s vision is expected to promote collaboration and understanding among the Church’s followers and beyond, promising an era marked by compassion and healing.