Pope Francis has appeared in St Peter’s Square in Rome ahead of the inauguration Mass that marks the official start of his papacy, the BBC reports.
Up to a million people, along with global political and religious leaders, are attending the Mass.
The first pontiff from the Americas, Francis has suggested he will take a more modest approach than predecessors.
Francis was elected by a conclave of cardinals last week to take over from Benedict XVI.
Benedict became the first pontiff in 600 years to abdicate last month. Citing his age, 85, he said he could no longer continue in the post.
Armenian President Serzh Sargsyan and His Holiness Karekin II, Supreme Patriarch and Catholicos of All Armenians, have also left for Vatican to participate in the Mass.