US Cardinal Robert Francis Prevost has been chosen as the new pope.
He was confirmed by senior cardinal Dominique Mamberti, who came out onto the balcony of St Peter's Basilica to cheering crowds.
Announcing the news, he said the famous Latin words "Habemus Papam", meaning "we have a pope," as thousands gathered in the square below.
Follow live updates: New pope elected
The 69-year-old Chicago-born cardinal will take the name Leo XIV, and in his first public words as pope, said: "May peace be with all of you."
Speaking of Pope Francis, who died on Easter Monday, the pontiff said: "The pope that blessed Rome gave his blessing to the whole world on that Easter morning. So let us follow up that blessing."
He then added: "Together, we must try to find out how to be a missionary church, a church that builds bridges, establishes dialogues.
"That's always open to receive, on this piazza with open arms, to be able to receive everybody that needs our charity, our presence, dialogue and love."
He went on to speak in Spanish, nodding to his time as a missionary, and said: "I would particularly like to say hello to my compatriots from Peru.
"It was a great pleasure for me to work in Peru."
Pope Leo then said: "Let us pray together for this new mission, for the whole church.
"And for peace throughout the world. And let's ask for this special grace from Mary, our mother."
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The new pontiff was chosen on the second day of the conclave after white smoke emerged from the Sistine Chapel at just after 5pm (UK time) on Thursday.
Some 133 cardinals gathered in Rome before being led into the Sistine Chapel on 7 May to start the conclave - the secretive process to decide the new pontiff.
They handed over their phones before entering the building, which had been swept for hidden cameras, recording equipment, and bugs.
The windows were also covered to keep the outside world out and to stop drones from spying.
Each cardinal swore an oath of secrecy. They did not emerge from the Vatican until the new pope was chosen.
To be elected, the new pontiff had to win a two-thirds majority (89 votes). Afterwards, he was asked whether he accepted the papacy and by which name he wished to be known.
When the pope was chosen, the ballots were burned in a stove with an additive to produce white smoke that billowed from a chimney to alert onlookers that the decision had been made.
Previously, the ballots were burned with an additive to produce black smoke, indicating that the pope had not yet been chosen.
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The election comes after Pope Francis died on 21 April at the age of 88 from a stroke and heart failure.
More than 250,000 people gathered at the Vatican for his funeral on 27 April.
(c) Sky News 2025: Cardinal Robert Francis Prevost becomes first American pope - and will take name of Leo XIV