The frail nun, who died in 1997 after spending more than six decades caring for the destitute and homeless, was beatified yesterday by Pope John Paul II at a two-hour long ceremony in Rome. Beatification is the final step on the path to sainthood.
Born Agnes Gonxha Bojaxhiu in 1910, in Skopje, the capital of modern-day Macedonia, Mother Teresa was the youngest of three children of an Albanian farmer.
At the age of 12, she realised she had a vocation helping the poor.
She joined the Sisters of Loreto, an order of nuns involved in education, and adopted the name of Sister Teresa in honour of Saint Teresa of Lisieux, the patroness of missionaries. After training for a few months in Dublin, Sister Teresa arrived in Calcutta, in January 1929.
For the next two decades, she taught in a private Catholic high school, but she could not ignore the widespread squalor and disease that she saw on the streets of the city.
In 1946, she was on a train to the mountain resort of Darjeeling hoping the mountain air there would cure her suspected tuberculosis when an overwhelming inspiration to change her life's work came over her.
Her new mission, she later recalled, would be "to serve the poorest of the poor". Then began her silent campaign of caring for the poor and ailing lepers shunned by society and the destitute who were dying in the gutters of Calcutta.
By 1949, she founded a new order, the Missionaries of Charity, and set up the first of a series of clinics for the homeless, named Nirmal Hriday or "Pure Heart".
Joined by a team of nuns, all dressed in the characteristic white saris with blue stripes that Mother Teresa adopted, she trawled Calcutta's fetid slums, picking up the dying and giving them food, medical care and shelter.
"I see God in every human being. When I wash the leper's wounds I feel I am nursing the Lord himself," she said in one interview in 1974.
Mother Teresa's selfless work earned her a Nobel Peace Prize in 1979.
"I choose the poverty of our poor people," she said in accepting the award in Oslo.
"But I am grateful to receive it in the name of the hungry, the naked, the homeless, of the crippled, of the blind, of the lepers, of all those people who feel unwanted, unloved, uncared for throughout society, people that have become a burden to the society and are shunned by everyone."
She used the Nobel cash award of US $192,000, along with dozens of other financial prizes and donations from foundations and private citizens, to help finance her charitable work, which spanned the globe.
She ministered to the hungry in Ethiopia, the radiation victims at Chernobyl, the survivors of a deadly earthquake in Armenia and residents of South Africa's squalid townships.
Since her death on September 5, 1997, Mother Teresa's message of compassion and caring has been carried on by the sisters of her order, which has grown to include 4,690 nuns who run 710 centres in 132 countries.
For many in India who witnessed her life's work, Sunday's beatification was a mere formality.
"The people of Calcutta had adopted her as a saint long before today," said Sandip Ghoshal, a shopkeeper in the city.