Pope Leo XIV gives his homily while celebrating his first Mass as pope with the cardinals who elected him in the Sistine Chapel at the Vatican May 9, 2025. (CNS photo/Vatican Media) VATICAN CITY (CNS) — Pope Leo XIV will officially inaugurate his papacy with Mass in St. Peter’s Square May 18.

Here’s what we know so far about Pope Leo’s inauguration Mass. The inauguration Mass is due to take place on Sunday, May 18, at 10 a.m. local time at St. Peter’s Square.

Then he did something notably uncharacteristic of Pope Francis. He sang. “Hallelujah,” he intoned reverently, in Latin. The moment spoke to an evolving truth. As much as Leo has echoed Francis since his dramatic debut on the central balcony Thursday,