Cardinal Jorge Mario Bergoglio, 76, of Argentina, has been named as the new Pope.
Cardinal Bergoglio, who is regarded as a surprise choice, will be known as Pope Francis, according to reports.
His dramatic election was signalled when white smoke billowed from the conclave of cardinals meeting in the Sistine Chapel.
Cardinal Bergoglio came second in the conclave which chose Pope Benedict, who retired last month.
He is the first Pope to be chosen from outside Europe for more than a millennium.
A stunned-looking Bergoglio shyly waved to the crowd of tens of thousands of people who gathered in St Peter’s Square, marvelling that the cardinals had had to look to “the end of the earth” to find a bishop of Rome.
He asked for prayers for himself, and for retired Pope Benedict XVI, whose resignation paved the way for the tumultuous conclave that brought the first Jesuit to the papacy.
The cardinal electors overcame deep divisions to select the 266th pontiff in a remarkably fast conclave.
Bergoglio had reportedly finished second in the 2005 conclave that produced Benedict – who last month became the first pope to resign in 600 years.
After announcing “Habemus Papum” – “We have a pope!” – a cardinal standing on the balcony of St Peter’s Basilica revealed the identity of the new pontiff, using his Latin name.
The 76-year-old archbishop of Buenos Aires has spent nearly his entire career at home in Argentina, overseeing churches and priests.
Tens of thousands of people who braved cold rain to watch the smokestack atop the Sistine Chapel jumped in joy when white smoke poured out, many shouting “Habemus Papam!” or “We have a pope!” – as the bells of St Peter’s Basilica and churches across Rome pealed.
Chants of “Long live the pope!” arose from the throngs of faithful, many with tears in their eyes. Crowds went wild as the Vatican and Italian military bands marched through the square and up the steps of the basilica, followed by Swiss Guards in silver helmets and full regalia.
They played the introduction to the Vatican and Italian anthems and the 50.000 strong crowd joined in, waving flags from countries around the world.
Elected on the fifth ballot, Francis was chosen in one of the fastest conclaves in years, remarkable given there was no clear front-runner going into the vote and that the church had been in turmoil following the upheaval unleashed by Pope Benedict XVI’s surprise resignation.
A winner must receive 77 votes, or two-thirds of the 115, to be named pope.
For comparison’s sake, Benedict was elected on the fourth ballot in 2005 – but he was the clear front-runner going into the vote. Pope John Paul II was elected on the eighth ballot in 1978 to become the first non-Italian pope in 455 years.