Jorge Mario Bergoglio, a 76-year-old from Argentina, was elected as the first Pope from outside Europe in more than a millennium -- the first from the Americas, taking the name Francis.
The new Pope, dressed in white vestments and with a crucifix around his neck, greeted the rapturous crowds at the end of a day of high drama.
Bergoglio was a hugely unexpected choice – he had not featured in any of the front-runner lists that were drawn up by Vatican watchers in the days before the election.
The appearance of the billowing white smoke from the tiny chimney on the terracotta tiled roof of the Sistine Chapel had earlier electrified Rome.
Within seconds, people were running up the broad avenue that leads from the banks of the River Tiber to St Peter's Square.
"They've chosen, they've chosen," a woman told her daughter as they hurried across rain-slicked cobbles.
Groups of young people cheered and sang and danced as tens of thousands of people made calls to friends and relatives.
They
waved flags and shouted "Viva Il Papa" – without yet knowing who Il
Papa was – as more and more people crammed into the square.
There
was then an agonising, excited wait of more than an hour in the
drizzle, as the massive crowd fizzed with speculation as to who the new
Pope might be before he emerged.
He was picked after the
cardinals cast just five votes in the papal conclave, held in the
frescoed splendour of the Sistine Chapel.
Marco Politi, a
well-known Vatican analyst, said: "I think it's a good move. He's not
Italian, he's not European, he's not a man of the Curia (the Holy See's
governing body). He represents an opening to the developing world.
"I
think Francis I signifies a completely new beginning. He's a moderate
man with some reformist tendencies. He's a man of the centre but open to
reform and to a more positive vision of the church."
His
decision to pick the name Francis was interpreted as a sign of his
desire to embrace simplicity and humility, in what could be an epic
shift for the church.
His personal style is said to be
the antithesis of Vatican pomp and the name he has chosen is fitting for
a man known for catching the bus and eschewing the luxuries of high
office.
He stepped out on to the balcony of St Peter's after a cardinal in scarlet robes had announced "habemus papum".
Bergoglio had reportedly finished second in the 2005 conclave that elected the German cardinal Joseph Ratzinger as Benedict XVI.
The Archbishop of Buenos Aires has spent nearly his entire career at home in Argentina.
He
asked for prayers for himself, and for his predecessor, the Pope
Emeritus, who is the first pope to step down willingly since 1294 and is
now living out his first weeks of retirement in a castle outside Rome.
The wait had finally come to an end at at 8.10pm local time.
The
white curtains behind the balcony of St Peter's were drawn aside, the
cardinal made his announcement in Latin, and the moment that the world
had been waiting for arrived.
The new Pontiff delivered
his first blessing to the giant crowd, asking for the prayers of "all
men and women of good will" to help him lead the Catholic Church.
Speaking with a slight Latin American accent, the man now known as Francis even cracked a joke.
"As
you know the duty of the conclave is to give Rome a bishop. It seems
that my brother cardinals went almost to the end of the world," a quip
which drew huge cheers and laughter from the rain-sodden crowd.