Brazilian President Dilma Rousseff waited on the tarmac for the pontiff to step down the stairs from the no frills commercial airliner that was specially booked for him.
It was the first time the Argentine-born Francis had returned to his home continent since his selection as pope in March.
Earlier on the flight from Rome, Francis expressed concern for a generation of youth growing up jobless as the world economy sputters.
The message should resonate with the young people in the mammoth crowds expected at a papal Mass on Rio's Copacabana beach and other ceremonies during Francis' seven days in Brazil, the world's most populous Roman Catholic nation.
During his stay, the 76-year-old Argentine-born pontiff will meet with legions of young Catholics converging for the church's World Youth Festival in Rio, a seaside Sin city better known for hedonistic excess. More than 1 million people are expected to pack the white sands of Copacabana for the Mass celebrated by Francis. He will also visit a tiny chapel in a trash-strewn slum, and make a side trip to venerate Brazil's patron saint, Our Lady of Aparecida.
The pontiff is expected to arrive in Rio de Janeiro at 3 p.m. EDT (1900 GMT) Monday.
During his flight from Rome, Francis warned about youth unemployment in some countries in the double digits, telling about 70 journalists aboard the papal plane that there is a "risk of having a generation that hasn't worked." He said, "Young people at this moment are in crisis."
He didn't specify any country or region, but much of Europe is seeing those gloomy youth joblessness numbers, especially in Greece, Spain and Italy. Brazil is in far better shape than European nations, with unemployment at an all-time low after a decade of economic expansion.
"I'm here for faith! I'm here for joy! And I'm here for the first Latino pope!" Ismael Diaz, a 27-year-old pilgrim wrapped in the flag of his native Paraguay, said as he bounded down the stone sidewalks of Copacabana hours ahead of Francis' arrival.
Diaz gave high fives to four fellow pilgrims, then turned toward local beachgoers who looked back at him while calmly sipping green coconut water and staring from behind dark sunglasses.
"I'm here because I have the force of God in me and want to make disciples of all. Arghhhhhhhhhh!" he yelled, lifting his head and howling into Rio's hot, humid air before flexing his arms and striking a bodybuilder's pose.
Alex Augusto, a 22-year-old seminarian dressed in the bright green official T-shirt for pilgrims, said Monday that he and five friends made the journey from Brazil's Sao Paulo state to "show that contrary to popular belief, the church isn't only made up of older people, it's full of young people. We want to show the real image of the church."
It would be easy for Francis if all Catholics shared the fervor of some of its younger members. But Diaz, Augusto and their fellow pilgrims are the exception in Brazil and much of Latin America, a region with more faithful than any other in the world but where millions have left the church for rival Pentecostal evangelical churches or secularism.
A poll from the respected Datafolha group published Sunday in the newspaper Folha de S.Paulo said 57 percent of Brazilians age 16 and older call themselves Catholic, the lowest ever recorded. Six years ago, when Pope Benedict XVI visited, a poll by the same firm found 64 percent considered themselves among the faithful. In 1980, when Pope John Paul II became the first pontiff to visit Brazil, 89 percent listed themselves as Catholics, according to that year's census.
Pentecostal evangelicals stood at 19 percent of the population in the latest poll, rising from virtually nothing three decades ago by aggressively proselytizing in Brazil's slums.
There is also a huge gap in the level of participation in the different churches, a fervor factor that deeply troubles the Catholic Church. The Datafolha poll said 63 percent of Pentecostal evangelicals report going to church at least once a week, while only 28 percent of Catholics say they attend Mass weekly.
Datafolha interviewed 3,758 people across Brazil on June 6-7 and said the poll had a margin error of 2 percentage points.
During his flight to Brazil, Francis also expressed concern about the elderly, saying older people should not be isolated or "thrown away ... as if they had nothing to offer us."
"A people has a future if it goes forward with bridges: with the young people having the strength to bring it forward and the elderly because they have the wisdom of life," the pope said. The elderly have "the wisdom of history, the wisdom of a nation, the wisdom of a family, and we need this."
Francis has spoken often of the need for humility in the church, and he kept to that message Monday; the pope carried his own black hand luggage as he boarded a special Alitalia flight from Rome.
"Every pope is different, and Pope Francis is showing himself to be extremely charismatic, with a language that is simple and direct," Sao Paulo Cardinal Odilo Scherer said.
Playing out alongside the papal visit is political unrest in Brazil, where widespread anti-government protests that began last month have continued and are expected to occur outside Rio's Guanabara Palace, the seat of state power where Francis is to meet with Rousseff later in the evening.
With the exception of gay rights groups and others angered by the church's doctrine against abortion and same-sex marriages, the target of most protesters won't be Francis but the government and political corruption. The pontiff is said to support Brazilians peacefully taking to the streets, and when he was a cardinal in Buenos Aires he didn't shy from conflict with Argentina's leaders as he railed against corruption.
When Francis talks with Rousseff, they are likely to focus on the poor. Upon taking office, the Brazilian leader declared that eradicating extreme poverty was her top goal as president, and she has expanded a network of social welfare programs that have helped lift almost 30 million Brazilians out of poverty in the last decade.
"Unlike his predecessors, who had a theoretical understanding, Francis has a pastoral understanding honed by living and working in working-class neighborhoods of Buenos Aires," said Joseph Palacios, a sociologist at Georgetown University and former Catholic priest who has studied the church.
That's evident to Maria Nascimento, a 60-year-old Catholic living in the Varginha slum that Francis will visit this week.
"God chose wisely when he decided to send this humble man to lead the church," she said, standing in her kitchen where photos of grandchildren's baptisms were stuck to her refrigerator with magnets.
"There's going to be a huge impact on Brazil after he has come and left, after his feet have walked these streets in our slum. He's going to help the church in Brazil, the love here for him is growing so fast."
Associated Press reporter Bradley Brooks reported from Rio de Janeiro. Jenny Barchfield contributed to this report.