Although presidents and princes attended the Mass in St Peter's Square, prisoners and migrants welcomed Francis' coffin at his final resting place in a basilica across town.
The Argentine Pope, who reigned for 12 years, died at the age of 88 on Monday after suffering a stroke.
According to Vatican estimates, about 250,000 people flocked to the funeral Mass at the Vatican and 150,000 more lined the motorcade route through downtown Rome to witness the first funeral procession for a pontiff in a century.
They clapped and cheered "Papa Francesco" as his simple wooden coffin travelled aboard a modified popemobile to St Mary Major Basilica, 6km away.
The scene resembled many popemobile rides Francis took in his 47 trips to all corners of the world.
As bells tolled, the pallbearers brought the coffin past several dozen migrants, prisoners and homeless people holding white roses outside the basilica.
Once inside, the pallbearers stopped in front of an icon of the Virgin Mary that Francis loved.
Four children deposited the roses at the foot of the altar before cardinals performed the burial rite at his tomb in a nearby niche.
"I'm so sorry that we've lost him," said Mohammed Abdallah, a 35-year-old migrant from Sudan who was one of the people who welcomed Francis to his final resting place.
"Francis helped so many people, refugees like us, and many other people in the world."
Earlier, Cardinal Giovanni Battista Re eulogised history's first Latin American pontiff during the Vatican Mass as a pope of the people, a pastor who knew how to communicate to the "least among us" with an informal spontaneous style.
"He was a pope among the people, with an open heart towards everyone," the 91-year-old dean of the College of Cardinals said in a highly personal sermon.
He drew applause from the crowd when he recounted Francis' constant concern for migrants, exemplified by celebrating Mass at the US-Mexico border and travelling to a refugee camp in Lesbos, Greece, when he brought 12 migrants home with him.
"The guiding thread of his mission was also the conviction that the church is a home for all, a home with its doors always open," Re said, noting that with his travels, the Argentine pontiff reached "the most peripheral of the peripheries of the world".
Despite Francis' focus on the powerless, the powerful were out in force at his funeral.
US President Donald Trump and former president Joe Biden, Ukrainian President Volodymyr Zelenskiy, United Nations Secretary-General António Guterres and UK Prime Minister Keir Starmer joined Prince William and continental European royals leading more than 160 official delegations.
Argentine President Javier Milei had pride of place given Francis' nationality, even if the two did not particularly get along and the Pope alienated some in his homeland by never returning there.
Trump sat with the rows of foreign dignitaries on one side of Francis' coffin in the vast St Peter's Square.
On the other side sat cardinals who will pick Francis' successor at a conclave next month.
Francis repeatedly called for an end to conflict during his papacy.
His funeral provided an opportunity for Trump, who is pushing for a deal to end Russia's war with Ukraine, to meet Ukrainian President Volodymyr Zelenskiy inside St Peter's Basilica.
Applause rang out as Francis' coffin, inlaid with a large cross, was brought out of the basilica and into the sun-filled square by 14 white-gloved pallbearers at the start of the Mass.
The crowds clapped loudly again at the end of the service when the ushers picked up the casket and tilted it slightly so more people could see.
Aerial views of the Vatican showed a patchwork of colours - black from the dark garb of the world's leaders, red from the vestments of 250 cardinals, the purple worn by some of the 400 bishops and the white worn by 4000 attending priests.
Francis, who shunned much of the pomp and privilege of the papacy, had asked to be buried at St Mary Major Basilica rather than in St Peter's - the first time a pope had been laid to rest outside the Vatican in more than a century.
with AP
