Cardinal Jorge Mario Bergoglio has been elected as the new Pope.
The 76-year-old - who was Archbishop of Buenos Aires in Argentina - will be the first ever leader of the Catholic Church from Latin America
He will be known as Pope Francis I.
A short time ago he addressed the thousands of well wishers in St Peter's Square:
Premier's Maria Rodrigues Toth in Rome descibed the scenes from the piazza in Vatican City:
Speaking on Premier Drive, Catholic expert Michael Cleere discussed Pope Francis' background as he walked out on the balcony to address the crowds for the first time:
Peter Williams from Catholic Voices has told Premier Pope Francis was an unexpected choice:
Meanwhile David Cameron's reacted to the election of a new Pope.
The Prime Minister's described it as a "momentous day for the 1-point-2 billion Catholics around the world".
White smoke was seen rising from the chimney of the Sistine Chapel at the Vatican just after 6pm GMT, signalling that Cardinals had chosen a new pope.
He'll replace Pope Benedict the 16th, who resigned last month.
The second ballot of the conclave failed to agree on a successor to Benedict XVI as black smoke emerged from the modest chimney of the Chapel this morning.
Jack Valero from the conservative Catholic group Opus Dei has told Premier no one expected a decision so soon:
Catholic journalist Austen Ivereigh says it appears the cardinals knew who they wanted to be Pope early on:
Speaking before the development, US Pastor, author and leading figure in the emerging church movement, Brian McLaren tells Premier how Americans are feeling about the voting process:
Crowds gathered again on Wednesday in Saint Peter's Square carrying their umbrellas and keeping a careful eye on the chimney perched on the roof.
One of them was Chris Bain, the Director of Catholic International Development charity CAFOD. He told Premier's Marcus Jones on the News Hour what his organisation is looking for in a new Pope:
Joseph Brunner, from near Munich, south Germany told Premier he drove through the night to get to St Peter's Square today:
During the conclave the cardinals live together and share rooms and are forbidden to watch television, listen to the radio or have any access to the internet.
US cardinal Timothy Dolan sent a tweet just a few hours before entering the conclave, saying:
"Greetings again from Rome, the Eternal City, the city of Saints Peter and Paul!"
But a new survey has revealed that more than half of us think the process of selecting the Pope should be more transparent and it needs up-dating. The ComRes poll, commissioned by Premier Christian Radio, revealed that 80% of the 2,000 people questioned thought that improving the reputation of the Catholic Church should be a key part of the new Pope's role. Premier's Maria Rodrigues-Toth is in Rome and says all the cardinals are locked in the chapel during the voting process and are sworn to secrecy:
The cardinals began their day with mass in the Pauline Chapel and then crossed the Sala Regia to the nearby Sistine Chapel.
In his homily yesterday, the Dean of the College of Cardinals, Cardinal Angelo Sodano, called for unity and said:
"We implore the Lord, that through the pastoral sollicitude of the Cardinal Fathers, He may soon grant another Good Shepherd to his Holy Church."
Benedict XVI stepped down last month saying he didn't feel he was mentally or physically capable of leading the Church.
He was the first Pope to resign in 600 years and it has thrown the Catholic church into turmoil and exposed deep divisions.