Pope Leo XIV, the first American pontiff for the Roman Catholic Church, will celebrate his inaugural mass on Sunday, according to the Vatican.

Pope Leo XIV presided over his inaugural mass Sunday, May 18, with world leaders and a crowd of 200,000 people gathered in St. Peter’s Square at the Vatican. Following the death of Pope Francis on April 21, a conclave commenced May 7, bringing together a private group of cardinals tasked with voting for a new leader of the Roman Catholic Church.