Pope John Paul II will oversee the fastest-ever process of beatification in a solemn ceremony expected to last around three hours.
Beatification will take the nun, treated as a saint during her life because of her humility and service to the world’s poorest, within scratching distance of full sainthood.
The best seat in the house during the ceremony will be occupied by Monica Basra, a 35-year-old Hindu woman whose claim that she was cured of stomach cancer by Mother Teresa set in train the process of beatification.
It was recognised as a miracle by Vatican investigators in 2002.
Mother Teresa with Pope John
Paul II in 1997
During the ceremony, Basra is due to walk up to the altar during the ceremony and kiss the pope's hand.
The congregation will also include dignitaries such as French Prime Minister Jean-Pierre Raffarin and Bernadette Chirac, wife of the French president.
In a central part of Sunday's ceremony, the pope will receive a vessel containing drops of Mother Teresa's blood from Sister Nirmala, the Indian nun who succeeded her as head of the Missionaries of Charity.
The blood is part of the “first class” category of relics that can be venerated in accordance with the rules of the Roman Catholic Church.
Vatican walkers help pope as he
arrives in St Peter's Square
This group includes a part of the body of a saint or blessed person, while a second category covers objects that belonged to them.
The relics will go on public display next week at the church of St John Lateran, while Mother Teresa's rosary beads, crucifix and tiny shoes have been on display for public veneration at a Rome church for the past week.
Still, to some extent, fears about the pope’s failing health have overshadowed the event, with many Catholics concerned that his battle with Parkinson's disease would sap his strength and force him to miss the event.
But many believe his personal friendship and admiration for the nun will probably fuel his determination to preside over the gruelling event.
After she died in 1997 at the age of 87, he said Mother Teresa was a "luminous example" for humanity in her care for the desperate and downtrodden.
The beatification mass, the biggest single event on the Church calendar this year, will start at 08:00 GMT, though pilgrims are likely to begin taking their places in the vast square long before dawn.
RAI Uno state television is to broadcast a biopic of the nun on Sunday and Monday, starring the actress Olivia Hussey as Teresa.