Pope Leo holding inaugural mass at the Vatican in front of thousands as crowds chant ‘Viva il Papa’

Pope Leo XIV will formally take up his role as leader of the global Catholic Church Sunday morning, with a Mass in St. Peter’s Square that has already drawn tens of thousands of well-wishers, including dozens of world leaders and European royalty.

After starting at St Peter’s tomb, on whose grave the Catholic Church is believed to be built, the ecclesiastical procession made its way to St Peter’s Basilica. The new pontiff was the last in the procession. He then addressed the hundreds of thousands watching the ceremony.

The pontiff took his first popemobile ride through St. Peter’s Square this morning, greeting the crowds who joined presidents, patriarchs and princes for the formal installation ceremony of history’s first American pope. An estimated 250,000 people are expected to turn out for the event.

The bells of St. Peter’s Basilica tolled as Leo waved from the back of the open-topped truck that looped slowly through the square and then up and down the boulevard to it.

The crowd cheered “Viva il Papa” and waved plenty of Peruvian, American and Holy See flags — representing Leo’s nationalities — mixed in with flags of other nations, banners and umbrellas to shield pilgrims from the springtime sun.

Security was tight as civil protection crews in neon uniforms funnelled pilgrims into quadrants in the piazza while priests hurried into St. Peter’s Basilica to get ready for the Mass.

Born in Chicago, the 69-year-old pontiff spent many years as a missionary in Peru and also has Peruvian citizenship. He becomes the first American pope and the first to have Peruvian citizenship. He was seen taking his first popemobile ride through St Peter’s Square earlier this morning ahead of his installation as thousands of fans waved at him.

Robert Prevost, a relative unknown on the world stage who only became a cardinal two years ago, was elected pope on May 8 after a short conclave of cardinals that lasted barely 24 hours.

He replaces Pope Francis, from Argentina, who died on 21 April after leading the Church for 12 often turbulent years during which he battled with traditionalists and championed the poor and marginalised.

US Vice President JD Vance, a Catholic convert who clashed with Francis over the Trump administration’s hard-line immigration policies, will lead a US delegation alongside secretary of state Marco Rubio, who is also Catholic.

Ukrainian President Volodymyr Zelensky is also in attendance, alongside his wife, Olena Zelenska, his chief adviser Andriy Yermak and foreign minister Andriy Sybiha. Mr Zelensky’s spokesperson suggested they were open to further peace talks in Rome after the ceremony, following the success of the Ukrainian president’s impromptu meeting with Donald Trump at Pope Francis’ funeral.

The inauguration Mass is a ritual filled with symbolism that connects back to Peter, Jesus’ apostle, and his special mission as head of the Catholic Church.

No new role is conferred but Leo will receive two crucial signs of his pontificate, the “pallium” and the fisherman’s ring, marking his role as successor of Peter.

The pallium is a narrow stole-like vestment with two pendants to be worn across the shoulders, decorated with crosses representing Jesus’ wounds. It’s made of white wool in an elaborate procedure where the lambs traditionally were blessed before being sheared, just like for the similar vestments given to archbishops on their ordination.

The fisherman’s ring recalls the Gospel passage where Jesus appeared to the apostles after his resurrection as they had spent a night fishing with no catch. He told Peter to cast in a specific spot— and the nets strained with lots of large fish, some of which the apostles then shared with Jesus in a lakeside breakfast.

An image of Peter with the net, standing for the church’s evangelization mission and its unity, is engraved on the ring alongside the pope’s name. When a pope dies, the ring is crossed over so it can no longer be used as seal for papal documents. Cardinal Luis Tagle of the Philippines, who was widely regarded as a papal contender, will present Leo with the ring.