Pope Francis has returned to the warm embrace of Latin America, landing in Brazil to begin his first international trip as pontiff.

Carrying his own hand luggage, Pope Francis flew from Rome to Rio on a no-frills commercial airliner that was specially booked for him.

It's the first time the Argentine-born Pope Francis has returned to his home continent since his selection as pope in March.

Waiting for him are 350,000 young Roman Catholics from 175 nations who are already in Rio for World Youth Day.

More than a million people are expected to pack the white sands of Copacabana to celebrate Mass with Pope Francis. He also will visit a tiny chapel in a rubbish-strewn slum, and grassroots Catholics love that he plans a side trip to venerate Brazil's patron saint.

Pope Francis arrives at a tough time for the church in Latin America, where it is losing faithful to rival churches and secularism.

A new poll says just 57 per cent of Brazilians aged 16 and older call themselves Catholics, the lowest recorded level.

In his few months as pontiff, the 76-year-old Pope Francis has demonstrated an easy ability to connect with people, in particular with young Catholics, demonstrating humility and a warmth the faithful feel is genuine. Church leaders hope his Brazil trip will deepen that appeal.

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 will not be Francis but the government and political corruption. The pontiff is said to support Brazilians peacefully taking to the streets, and when he served as a cardinal in Buenos Aires he didn't shy from conflict with Argentina's leaders as he railed against corruption.

The pope will likely avoid hot topics like abortion and same-sex marriages while in Brazil, and focus on his message that the church should put its attention on the poor and that clergy must lead a humble life.

The Catholic Church is not as active in politics in Brazil as it is in other Latin American nations, though it strongly opposes any efforts to loosen abortion laws and took part in the legal argument against civil unions when the matter was before the top court.