Speaking before a vast crowd, Pope John Paul has beatified Mother Teresa of Calcutta, putting the "Saint of the Gutters" on the fast track to sainthood for her life of selfless help to the poor.
"With our apostolic authority, we grant that the venerable servant of God Teresa of Calcutta shall from now on be called blessed," declared the pontiff, a longtime friend of the nun who died in 1997 at the age of 87.
Applause and cheering broke out in the crowd of more than 150,000 and a large tapestry showing a smiling Mother Teresa was unveiled from a balcony of Christendom's largest church.
The crowd, made up of Catholics and non-Catholic admirers, packed St Peter's Square and filled the broad Via della Conciliazione leading from the Vatican to the River Tiber.
Educated in Ireland, the ethnic Albanian sister, winner of the 1979 Nobel Peace Prize, tended the sick and dying of Calcutta's slums for decades with the Missionaries of Charity order she founded.
Many of her nuns in their blue-trimmed white saris stood out in the vast crowd, where a special section for thousands of Rome's homeless and downtrodden was reserved close to the elevated altar where the pope said the beatification Mass.
"Mother Teresa was for us great because she was not just a daughter of our homeland, Albania. She gave up our flag and every other flag for one flag, the flag of love," said Dod Brokshi, an Albanian who came with his family.
"Coming here means a new renaissance for us," he said, waving the red Albanian flag emblazoned with a black eagle.
While she never hid her Christian inspiration, the nun won admiration from Hindus, Muslims and other non-Catholics around the world.
"It is not enough for us to say: I love God, but I do not love my neighbour... How can you love God whom you do not see, if you do not love your neighbour whom you see, whom you touch, with whom you live?" she said in her 1979 Nobel Peace Prize acceptance speech.
A frail figure, she became the world's most famous nun for decades of work among the sick and dying, the homeless and the lepers in the Indian city of Calcutta, one of the most impoverished on earth.
She launched her Missionaries of Charity order in 1950 with 12 nuns. It has grown to 4,500 sisters in 133 countries running homes, schools and hospices for the poor and dying.
The 83-year-old pope, suffering from Parkinson's disease which is taking an increasingly visible toll on his health, so admired her that he bent Vatican rules to rush her towards sainthood.
The Polish pontiff granted a dispensation so the procedure for establishing her case for sainthood could be started two years after her death instead of the normal five years.
He even considered bypassing normal procedures and making a saint immediately of Mother Teresa, who was born in Skopje in what is now Macedonia. But cardinals advised against it, saying it would set a precedent difficult to manage in the future with other candidates for sainthood.
Before beatification the Church requires proof that a candidate performed one miracle. Proof of a second one is needed before canonisation as a saint.
The first miracle formally attributed to her concerned a young Indian woman, Monica Bersa, whose stomach cancer tumour shrank after she prayed to her in 1998, baffling doctors.
"I am fine now. It is all due to the blessings of Mother Teresa," Bersa told Reuters last year in Danogram, some 360 km (220 miles) north of Calcutta.
A commission of doctors examined the case and said they had no ready explanation in medical science for the cure.
Born Agnes Gonxha Bojaxhiu on August 26, 1910, Mother Teresa was sent to India in 1928 as a young Sister of Loreto, an Irish community of nuns with a mission in Calcutta.
She taught in the order's schools for two decades before leaving to devote herself to work in Calcutta's notorious slums.