Dignitaries from around the world, including Vice President JD Vance joined an estimated 200,000 people in and near St. Peter’s Square to watch the first American pope officially start his papacy.

Pope Leo XIV appeared to get emotional as he celebrated his inaugural mass before 200,000 faithful.

Pope Leo XIV and U.S. Vice President JD Vance are meeting ahead of a flurry of U.S.-led diplomatic efforts to make progress on a ceasefire in Ukraine

An open-topped popemobile carrying Pope Leo XIV drove through St Peter's Square at the Vatican on Sunday morning, ahead of his inaugural mass.

On “This Week,” ABC News’ correspondent Maggie Rulli reports on Pope Leo XIV’s inaugural mass.

About 100,000 people gathered in St. Peter's Square to watch the mass, according to the Vatican's press office.

ABC News’ Maggie Rulli reports from Vatican City as the first Roman Catholic pope from the U.S. formally took over as the leader of the church and greeted the faithful in the popemobile.

Pope Leo XIV has offered the Vatican as a location for peace talks between Russia and Ukraine.

Vice President JD Vance and Secretary of State Marco Rubio will be two of many global leaders in attendance of Pope Leo XIV’s inaugural Mass at the Vatican.

Pope Leo XIV, the first American pontiff for the Roman Catholic Church, will celebrate his inaugural mass on Sunday, according to the Vatican.

Sunday's mass will mark the official start of Pope Leo's papacy. He is expected to ride through the square in the popemobile for the first time.

Pope Leo XIV has met at the Vatican with the head of the Greek Catholic Church in Ukraine

What Pope Leo XIV Told ABC'S Terry Moran and James Longman about his brothers back in the U.S.

On "This Week," Cardinal Cupich said Pope Leo XIV may call for changes to the United States immigration system.

Francis Rooney, former U.S. Ambassador to the Holy See, expects that his friend of decades will "talk about the human condition a great deal" as pope.

The new pope talked about the importance of freedom of speech and renewed calls for peace during a meeting with journalists on Monday.

Pope Leo made his first Sunday address from the balcony overlooking St. Peter's Square. ABC News' James Longman reported from Rome.

The pope declared "Never again war" while addressing crowds in St. Peter's Square on Sunday.

On “This Week,” ABC News’ Terry Moran, WLS’ Liz Nagy and Father James Martin break down the significance of the selection of Pope Leo XIV.

On “This Week,” ABC News’ Chief International Correspondent James Longman reports on the first American pope.

On “This Week,” ABC News’ Correspondent Matt Rivers reports from Chiclayo, Peru, where Pope Leo XIV served his ministry.

St. Turibius Parish in Chicago Rev. William Lego joins ABC News Live to discuss growing up with Pope Leo XIV, and their friendship.

ABC News’ Martha Raddatz interviews Archbishop of Chicago Cardinal Blase Cupich on “This Week.”

ABC News’ Martha Raddatz interviews the Rev. Peter Donohue on “This Week.”

Thousands of people gathered on Sunday to see the first American pope deliver a traditional prayer from the balcony of St. Peter’s Basilica in Vatican City.

The new pope Leo XIV is scheduled to deliver his first Sunday blessing from the loggia where he first appeared in public after being elected three days ago

Pope Leo made his first trip outside of the Vatican, stopping at the tomb of his predecessor, Pope Francis, laying a single white rose.

Father Arthur Purcaro, the assistant vice president of mission and ministry with Villanova University, reflects on his relationship with newly-elected Pope Leo XIV.

Pope Leo XIV is now the most powerful American Catholic in the world, and experts say he must aptly walk the line between U.S. politics and his papal duties.

Pope Leo XIV might be "gringo" by birth but ask the people from Chiclayo, Peru, and the man is decidedly Peruvian.

ABC News' Maggie Rulli takes a look at what a Pope Leo XIV papacy may look like.

Brothers of Pope Leo XIV share more about how he was shaped by his faith at an early age.

Less than 24 hours after being introduced as pope, Leo XIV celebrated his first mass and spent time with the faithful, giving out blessings.

David Muir shares some of the most memorable images of the past two days after the historic election of the first American pope.

In his first mass since becoming pope, Pope Leo XIV reaffirming his pursuit for unity as many describe him as a bridge builder.

Francis Rooney, former U.S. Ambassador to the Holy See, reflects on the time he spent with Cardinal Robert Prevost before he was elected as Pope Leo XIV.

Pope Leo XIV's family tree reflects America's complex racial history, according to records obtained by ABC News.

Despite historic gains under Pope Francis, women remain excluded from the Catholic Church's highest levels of decision-making.

Genealogist and founder of Unearthing Your Roots, Chris Smothers, traced Pope Leo XIV's family tree which showed a reflection of America's complex racial history.

Friend of Pope Leo XIV, Father Robert Hagan, joined ABC News Live to talk about what to expect from the new American born pontiff.

Pope Leo XIV is registered to vote in the United States and has previously voted in some Republican primaries, but he is not registered as a member of a political party.

Harry Styles was photographed by eagle-eyed onlookers in Rome on Thursday as Pope Leo XIV was elected the new pontiff.

Following the election of Pope Leo XIV, the first pontiff elected from the U.S., American cardinals shared their reaction to the new leader of the church.

Sister Barbara Reid, president of the Catholic Theological Union, celebrated Pope Leo XIV as the first pope chosen from the U.S.

The newly elected Pope Leo XIV could continue in his predecessor's footprints as the steward of the environment of the Catholic Church.

Timothy Dolan, archbishop of New York, said he did not think the fact that Pope Leo was from the U.S. "carried much weight" in the decision to elect him as the leader of the Roman Catholic Church.

Kevin Hughes, chair of theology and religious studies at Villanova University, discusses Pope Leo XIV’s alma mater celebrating Robert Prevost becoming pontiff.

Somos Community Care founder and chairman Dr. Ramón Tallaj talks about the similarities between the two pontiffs.

When Cardinal Robert Prevost was in the first grade, his neighbor told him he would be the first American pope, his brother told ABC News.

Rev. Mark Francis was a former high school and college classmate of Robert Prevost, the man who would become Pope Leo XIV.