While she is famed for her work with the poor in the Indian city of Kolkata, the late missionary's origins have been hotly disputed in southeastern Europe, where she grew up. Her father's roots are more debated: most people, especially in Albania, say he too was ethnically Albanian, although some Macedonians have argued he was a Vlach, another Balkan ethnic group.
Born Agnes Gonxha Bojaxhiu in 1910 in multi-cultural Skopje-then part of the Ottoman Empire and now capital of the Republic of Macedonia - Mother Teresa had an ethnic Albanian mother whose family came from Kosovo.
The squabble exposes old ethnic rivalries in the Balkans, with neighbours Albania and Macedonia taking competitive pride in the Nobel Peace Prize winner-both countries have statues, roads, hospitals and other monuments in her name.
"Mother Teresa was born in Skopje but she never declared herself a Macedonian," said Albanian historian Moikom Zeqo, author of a study on the nun's links to Albania. She "always spoke about her Albanian origins and her universal mission," Zeqo told AFP. Macedonians, however, suggest her birthplace is all important.
"We call her 'Skopjanka' (citizen of Skopje) because we know she is ours," said Valentina Bozinovska, director of the national commission for relations with religious communities.
The region changed dramatically in Teresa's lifetime, with the end of Turkish rule, two world wars, the rise and fall of communism and Yugoslavia, and the nationalistic Balkan wars of the 1990s.
Teresa was baptised Roman Catholic, a minority religion in Skopje, where she spent her childhood and decided early on she would take up a religious life. She left home aged 18 for a spell at an Irish abbey before travelling to India in 1929. In the 1930s her mother and sister moved to Tirana in Albania, where communist dictator Enver Hoxha barred Teresa from visiting.
She eventually made her first of three trips to Albania in 1989, after Hoxha's death and a year before communism began to fall, to visit the graves of her family and the house where they lived for many years. Genc Zajmi, 78, still resides in the building and recalls Teresa's loving letters to her mother, insisting the nun never forgot her Albanian roots.
Muslim-majority Albania celebrates a public holiday on the anniversary of Teresa's beatification in 2003. As for Teresa, she was quoted describing herself both as a "Skopjanka" and as an Albanian "by blood", but insisting she belonged to the world.
Her adopted home country is India-which gave her citizenship in 1951 - flatly refused Albania's request in 2009 to hand over her remains, saying she was "resting in her own country, her own land".
While she is famed for her work with the poor in the Indian city of Kolkata, the late missionary's origins have been hotly disputed in southeastern Europe, where she grew up.
Her father's roots are more debated: most people, especially in Albania, say he too was ethnically Albanian, although some Macedonians have argued he was a Vlach, another Balkan ethnic group.