By STACY MEICHTRY, ALESSANDRA GALLONI and DAVID LUHNOW

VATICAN CITY—The Roman Catholic Church’s leaders elected their new pope Wednesday in a day that was rich in ritual but broke with tradition—placing the world’s 1.2 billion Catholics under the direction of a Jesuit from the New World, both firsts in Christianity’s 2,000-year history.

 

Argentina’s Cardinal Jorge Mario Bergoglio, the 76-year-old archbishop of Buenos Aires, emerged on the balcony of St. Peter’s Basilica here Wednesday evening and was introduced as Pope Francis. A crowd of more than 100,000 pilgrims in the square below sounded cheers of “Viva il Papa” as he urged a “great fraternity” for the global church.

 

His election places the church under the leadership of a man who is known less as an educator or intellectual, as was his predecessor, but as a humble and mild-mannered shepherd of his flock. The choice of a man who has shunned the lofty trappings of a cardinal—and has spent relatively little time in the corridors of the Vatican—is likely to have broad resonance at a time when Catholicism has been losing credibility and followers in many parts of the world.

 

The selection of the first pontiff from the Americas is the second groundbreaking event for the Catholic Church in one month. Pope Francis’s predecessor, Benedict XVI, who stepped down on Feb. 28, was the first pontiff in more than six centuries to resign from a position traditionally held until death.

 

“Brothers and sisters, good evening. … Good night, and have a good rest.” Pope Francis’ Greeting and Last Words to the Crowd Wednesday

Pope Francis immediately embraced his mission as shepherd in Rome and the world. Appearing with outstretched arms on St. Peter’s main balcony, he led the pilgrims below in the Lord’s Prayer and then asked them for a favor: a moment of prayer for him. He also joked with the crowd about how far he had come to be their pope.

 

“As you know, the duty of the conclave is to give Rome a bishop,” he said. “It seems that my brother cardinals went almost to the end of the earth to find him.”

 

His election also breaks new ground for the Society of Jesus, known as Jesuits, a religious order renowned for its skepticism of authority and hierarchy. St. Ignatius Loyola, the order’s founder, “didn’t want Jesuits to be bishops, because he didn’t want prestige and power associated with it,” said the Rev. Joseph Fessio. “He wanted them to work as priests.”

 

What is unclear is whether the new pope, who has no experience with the central administration of the Vatican, will be adept in tackling some of the problems that face the so-called Curia. The Vatican’s central administration has for long been seen as ineffective in governing Catholicism’s sprawl. A recent scandal, in which secret documents were leaked to Italian media, has also exposed rifts among top Vatican officials.

 

Pope Francis is likely to follow the traditionalist path of continuing the teaching of his predecessor, who believed that the way to stem the wave of secularism was to stand defiantly against it, analysts said. “Certainly there will be continuity in the teaching of the church,” said Father Fessio, a Jesuit and former student of Benedict XVI.

 

In many ways, Cardinal Bergoglio is an ideal figure to transition from a centuries-old line of European popes. His father was an Italian immigrant, giving him roots in a country that is, along with Spain, considered a mother country of Argentina. It is often said that Argentines speak Spanish with an Italian flair. That cultural affinity may have helped Cardinal Bergoglio with many of his Italian peers that dominate the Curia.

 

His first moments as pope were reminiscent of those of John Paul II, whose personal warmth shone when he came out in 1978 and asked the crowd to be patient with his Italian. Pope Francis, though, spoke in crisp Italian with a slight Spanish accent. “Let us start this journey…which leads all the churches in charity, a journey of fraternity, of love, of trust among us,” he said.

 

The election of the new pope was announced to the world—as is tradition of the church—with a vigorous puff of white smoke from the smokestack of the Sistine Chapel, where 115 cardinals had been sequestered since Tuesday evening to pick Catholicism’s new leader.

 

Though the conclave is conducted amid high secrecy, there had been ardent speculation that this one would end quickly. That is because, unlike past conclaves that follow the unexpected death of a pope, the resignation of Benedict XVI had been announced on Feb. 11, giving cardinals time to reflect.

 

In anticipation, tens of thousands of people had been gathering in St. Peter’s Square despite the heavy rain Wednesday. When the puffs turned a definitive white against the backdrop of a pitch-black evening sky, they let out a collective roar.

 

While Cardinal Bergoglio hadn’t been named among the favorites ahead of the conclave, he had come close to being elected in 2005, during the conclave that elected Benedict XVI, said one cardinal who had been present then. While several cardinals had initially tapped Cardinal Bergoglio as a possible successor to John Paul II, a majority coalesced around the then-Cardinal Joseph Ratzinger. At the time, Cardinal Bergoglio then made it clear that he did not want to be an “opposition candidate,” this cardinal said.

 

The selection of a Latin American pope underscores a big demographic shift in the Catholic Church toward the region. A century ago, 65% of the world’s Catholics lived in Europe. But by 2010, only 24% did, according to demographer Conrad Hackett at the Pew Research Center’s Forum on Religion and Life. Meantime, Latin America’s share has risen to 39%—more than Europe and U.S. combined.

 

But overall, the story of the Latin American church has been one of decline. Whereas the region was more than 90% Catholic some 50 years ago, today there are countries in Central America where fewer than half are today.

 

One-room evangelical churches now dot the Latin American landscape, from remote Amazon villages to the labyrinthine slums that surround the poor-region’s major cities.

 

“No other region is as important to the future of the Church, or could use an intervention, as much as Latin America,” said Andrew Chesnut, who holds the Bishop Walter Sullivan Chair in Catholic Studies at Virginia Commonwealth University and has written several books on Christianity in Latin America. “This is a recognition that that future of the church lies in the global south.”

 

Eugenio Lira, secretary general of the Mexican Episcopal Conference and auxiliary bishop of Puebla, expressed excitement at Latin America having its first pope, describing Cardinal Bergoglio as “a man of enormous modesty.”

 

“He will be able to better understand the Latin American continent, not only the poverty and the exclusion, but also the wealth of these lands,” said Mr. Lira.

 

To reverse the trend away from Catholicism, the church is naming more Latin American saints. In 2002, the John Paul II canonized the first native American saint, Juan Diego, a 15th century Indian whose vision of the Virgin of Guadalupe is emblematic of the Catholic faith in Mexico. In 2007, Pope Benedict XVI canonized the first Brazilian-born saint, Saint Anthony of Saint Ann Galvão, an 18th century friar and healer.

 

“There are two types of men: those who take care of the pain and those who pass by” – From a 2003 Homily as Argentina’s Néstor Kirchner Took Office

In Buenos Aires, hundreds of people gathered outside the cathedral in the Plaza de Mayo, considered the heart of the country. Gabriel Llorens, a churchgoer who has followed Cardinal Bergoglio for years, said he was elated to see an Argentine and someone from Latin America become pope.

 

“This is very emotional as an Argentine, as a Catholic, and as someone who appreciates the church. It’s incredible,” said Mr. Llorens, who has volunteered with the church.

 

With his pastoral approach, Pope Francis represents a drastic change from the doctoral style of Benedict XVI, said Alberto Melloni, a church historian at the University of Modena and Reggio Emilia. “His simplicity can fix all the problems of the Church at once.”

 

“What emotion! ” said Gladys Suarez, an Uruguayan who has lived 37 years in Argentina, as she waived flags of both countries. “Who would have thought—a Latin American pope!

—Giada Zampano and John D. Stoll contributed to this article.

Write to Stacy Meichtry at stacy.meichtry@wsj.com, Alessandra Galloni at alessandra.galloni@wsj.com and David Luhnow at david.luhnow@wsj.com