The 76-year-old was welcomed by tens of thousands of overjoyed Catholics in St. Peter's Square in the Vatican City after his election was revealed when white symbolic smoke poured out of the Sistine Chapel's chimney.
Pope Francis becomes the first South American Pontiff and the first Jesuit to lead the Catholic Church.
His South American origin - also making him the first non-European Pope - is a significant move for the Church, taking the Papacy to a continent in which 42 per cent of the world's Catholics live amid a plethora of recent scandals affecting the Vatican.
Known as an avid reformer, he becomes the third non-Italian Pope in a row, having being born and spent his life in the Argentinian capital.
Dressed in white robes with an elaborate stole, he said: 'First and foremost I would like to pray for our emeritus Pope Benedict XVI that Christ and the Madonna watch over him.
'Let us being this journey together, this journey for the Roman Catholic Church. It's a journey of friendship and love and faith between us. Let us pray for one another, let us pray for all the world.'
He then asked the crowd to be silent for a moment and pray for him as he accepted his new position. 'I'd ask you to pray to God so that he can bless me,' Pope Francis said, leading a silent prayer, followed by a loud cheer from the crowd.
He said that the world 'should set off on a path of love and fraternity', leaving the address by saying to the crowds: 'Good night and I wish you a peaceful rest.'
The Vatican said he chose the name Francis after St. Francis of Assisi, who formed the Franciscan order, saying that the new Pope is a 'lover of the poor'.
The native Spanish speaker is multilingual, also speaking German and Italian. He courted controversy in 2005 when a human rights lawyer filed a criminal complaint against him accusing the cardinal of conspiring with the Argentinian junta to kidnap two Jesuit priests in 1976.
The military junta took charge of the country after Isabel Peron was overthrown by a right-wing coup.
In his role as superior of the Society of Jesus of Argentina that year, the cardinal had allegedly asked the priests to leave their pastoral work following conflict within the Society over how to respond to the new military dictatorship.
Pope Francis is the first Jesuit Pope, the collective name given to members of the Society of Jesus, the largest order of priests and brothers in the Catholic Church.
Tens of thousands had cheered in St.Peter 's Square at the sight of the symbolic plumes, announcing that the successor to Benedict XVI had finally been chosen after two days of intense voting.
The first tweet of Francis I’s reign, posted on the papal Twitter account Pontifex, read: ‘HABEMUS PAPAM FRANCISCUM’, meaning ‘We have Pope Francis’.
On his personal account, he tweeted shortly after the decision, writing: 'Perhaps a little humility in saying I am simply representative of God on Earth, just as God is representative of me in Heaven.'
He followed this 20 minutes later with a message saying 'Extremely happy to be the new Pope, Francisco I'.
THE SON OF A RAILWAY WORKER WHO WAS ACCUSED OF CONSPIRING WITH THE ARGENTINIAN JUNTA
Pope Francis - the first Jesuit pope - has spent nearly his entire career at home in Argentina.
The former Jorge Mario Bergoglio, 76, reportedly got the second-most votes after Joseph Ratzinger, the last pope, in the 2005 papal election.
He has long specialised in the kind of pastoral work - overseeing churches and priests - that some say is an essential skill for a pope.
In a lifetime of teaching and leading priests in Latin America, which has the largest share of the world's Catholics, the former Bergoglio has shown a keen political sensibility as well as a self-effacing humility, according to his official biographer, Sergio Rubin.
His personal style is the antithesis of Vatican splendor. Bergoglio is also known for modernising an Argentine church that had
been among the most conservative in Latin America.
He chose the name Pope Francis I, after St Francis of Assisi and is the first pope from the Americas and the first from outside Europe in over a thousand years.
He was born in Buenos Aires, one of five children of an Italian railway worker and his wife and was ordained to the priesthood in 1969.
On April 15, 2005, a human rights lawyer filed a criminal complaint against Bergoglio, accusing him of conspiring with the junta in 1976 to kidnap two Jesuit priests, whom he, as superior of the Society of Jesus of Argentina in 1976, had asked to leave their pastoral work following conflict within the Society over how to respond to the new military dictatorship, with some priests advocating a violent overthrow.
Bergoglio's spokesman has flatly denied the allegations. No evidence was presented linking the cardinal to this crime.
Of all the contenders to replace Pope Benedict XVI, Cardinal Jorge Mario Bergoglio of Buenos Aires was little mentioned.
The 76-year-old reportedly received the second most votes after Joseph Ratzinger, the last pope, in the 2005 papal election.
And as a representative of South America's Catholics - who make up an estimated 40 per cent of the 1.2 billion strong church, he was widely supported on a massive scale.
He became Pope Francis after a surprisingly quick conclave winning 77 votes, or two-thirds of the 115 cardinals' votes, on the fifth ballot.
His decision to pick the name Francis evokes key Christian tenets such as simplicity and humility.
And they are fitting for a man who, spending nearly his entire career in Argentina, is known for catching the bus and eschewing the luxuries of high office.
His personal style is said to be the antithesis of Vatican splendour.
Pope Francis has been described by commentators as a voice of conscience and a reconciler.
Classed by some as a moderniser of a strict South American church, he is still conservative and an opponent of such ideas as gay marriage.
Prominent figures from the world of politics and religious leaders began to send their regards to the new Pontiff last night.
David Cameron tweeted: ‘A momentous day for the 1.2bn Catholics around the world as His Holiness Pope Francis I is appointed the 266th Bishop of Rome.’
US President Obama offered his warm wishes to the new Pope and said the choice of a Latin American ‘speaks to the strength and vitality of an increasingly-important region’.
UN general Secretary Ban Ki-Moon Ban Ki-moon congratulated Pope Francis via Twitter, saying he is looking forward to continued cooperation between the UN and the Holy See.
Catholic Archbishop of Westminster Vincent Nichols, president of the Catholic bishops' conference of England and Wales, said: ‘As he begins his new apostolic ministry, as the Bishop of Rome and shepherd of the universal Church, Pope Francis I may be assured of the prayers and loving support of the Catholic community throughout England and Wales.'
After hours braving the cold rain, the huge crowd in the Vatican City chanted 'Habemus Papam' and 'We have a pope' - as the bells of St. Peter's Basilica and other churches across Rome pealed at news of the election.
With excitement building before the Pope Francis's imminent appearance on the loggia, the crowd repeated the refrain 'Viva il Papa' - translated as 'Long live the Pope'.
The new Pope was dressed in his papal robes and joined in prayer with the other cardinals before his appearance.
The conclave was called after Pope Benedict XVI resigned last month for health reasons, sending the church into turmoil and exposing deep divisions among cardinals tasked with finding a replacement to address issues within the church.
WAS CHOICE OF NAME HOMAGE TO THE SAINT WHO FOUNDED THE FRANCISCAN ORDER?
The Vatican last night said it was a homage to St. Francis of Assisi, the 13th century Italian founder of the Franciscan order, describing him as a 'lover of the poor'.
The number 'I' makes it clear that there never has been a Pope Francis before – though there have been a number of saints to bear this name.
St Francis of Assisi is a man who turned his back on power and wealth to dedicate himself to a radical life of Christian poverty, evangelisation and peace-making.
St Francis was so holy that, according to Catholic belief, he received the stigmata, the five wounds of Christ, in his own body while still alive.
The attraction of taking the name of a man who founded a religious order may be strong given that the new Pope is a member of an order himself.
He belongs to the Jesuits, or the Society of Jesus, which for the 400 years the most popular order in the Catholic Church and its members were known for the bravery and academic excellence.
During the Protestant Reformation, the Popes sent Jesuits on the English Mission to build up the Catholic Church under the noses of the Elizabethan authorities.
Many of them – such as St Edmund Campion and St Robert Southwell – shed their blood on the scaffold of Tyburn and they have also died as martyrs in many other countries of the world.
They grew so powerful that the heads of the Jesuits were known as the ‘black pope’ and were suppressed in the 18th century after their opposition to slavery infuriated the royal houses of France, Spain and Portugal.
The choice of the name of the new pope may also be connected to one of the first Jesuits – St Francis Xavier – a close colleague of the 16th founder, St Ignatius of Loyola.
St Francis was a missionary who took the Catholic faith to India and the Far East after Ignatius persuaded him to turn his back on a medical career.
The missionary zeal might indicate the ambitions of Pope Francis as the Catholic Church is confronted with the crisis of the loss of faith and is once again redoubling its efforts to win souls for Christ – but this time in the secular West'
They were followed by Swiss Guards, dressed in silver helmets and full regalia.
A result on only the first full day of voting in the Papal election surprised many, with the process expected to take several days.
This was due to there being no clear frontrunner in the election of the 266th Pontiff, while it was also expected the conclave would be longer as the previous Pope had not died.
The election of Pope Francis required one more ballot than Joseph Ratzinger's election process in 2005 in what was one of the quickest elections of all time.
On the first evening of that election black smoke appeared from the Sistine Chapel’s chimney before a further two votes the following morning did not get a result either. However the third ballot saw Benedict XVI elected after only 26 hours of debate"