Pope Francis has officially begun his papacy as the 266th pontiff, receiving the ring symbolising the office and a wool stole ('pallium') symbolising his role as shepherd of his 1.2-billion strong flock.
World leaders and tens of thousands of pilgrims are in the square for today's ceremony.
A cardinal intoned the rite of inauguration at the start of today’s Mass, saying: “The Good Shepherd charged Peter to feed his lambs and his sheep; today you succeed him as the bishop of this church.”
Later half a dozen cardinals approached the Argentine-born Pope to pledge their obedience.
The pallium is a strip of lambswool that represents the Pope's role as a shepherd and the Fisherman's Ring is named in honour of the first pope St Peter, a fisherman by trade.
Earlier the Pope toured St Peter's Square in an open-top car making a a couple of unscheduled stops to bless pilgrims.
The installation occurred in sun-drenched St Peter’s Square in front of tens of thousands of people, princes, sheiks, rabbis and presidents.