The Queen led the messages of sympathy from around Britain after Mother Teresa, the Nobel Peace Prize winner who devoted her life to helping the sick and the poor, died at the age of 87.
She suffered a heart attack at the headquarters of the Missionaries of Charity in Calcutta on September 5, 1997.
The Queen said the Roman Catholic nun had been an inspiration who would live in the hearts of those who had been touched by her.
Mother Teresa had been battling ill health for some years, and in March had stepped down as head of the order of nuns she founded.
The Queen said: “It was with deep sadness that I learnt this evening of the death of Mother Teresa.
“Her untiring devotion to the poor and destitute of all religions has been an inspiration worldwide.
“She will continue to live in the hearts of all those who have been touched by her selfless work.”
Born Agnes Goinxha Bejaxhiu to Albanian parents in Skopje, Mother Teresa formed an order of nuns dedicated to helping the world’s neediest people.
She became known around the globe for her compassion and was portrayed as a beacon of humanity by the media.
But her role during her later years was hampered by her increasing frailty.
Last year she celebrated her birthday from a hospital bed and was unable to speak because of respiratory tubes fitted to help her overcome her breathing problems.
She was initially admitted to hospital with a bout of malaria but later developed heart, kidney and lung trouble.
But she staged a miraculous recovery and went on a tour of Europe and the US with her successor, Sister Nirmala, in May this year.
When told she had won the Nobel Peace Prize in 1979 for bringing hope and dignity to millions of unwanted people, she said: “I am unworthy.”
“The poor must know that we love them,” was her simple message.
She said her divine call to work among the poor had come in 1946 and opened her first Calcutta slum school in 1949.
She took the name Teresa, after France’s St Therese of the Child Jesus. In India, she was simply “Mother”.
World leaders were among those paying tribute to Mother Teresa.
“This evening, there is less love, less compassion, less light in the world,” said President Jacques Chirac of France.
President Clinton praised her as an “incredible person” and “one of the giants of our time”.
In India, prime minister Inder Kumar Gujral said: “Words fail me to express my sorrow. An apostle of peace and love, Mother Teresa is no more with us.”
Italian prime minister Romano Prodi called Mother Teresa “a luminous example of love for one’s neighbour and of living charity”.
The Vatican said the Pope planned to hold a special mass at Castel Gandolfo, his summer residence outside Rome.
A spokesman told reporters he was "deeply hurt" by the news of her death.
"The Pope believes she is a woman who has left her mark on the history of this century," he said.
The head of the Catholic church in England and Wales, Cardinal Hume, said she was an "enormously significant figure - everyone knows who Mother Teresa is".
Irish President Mary Robinson said: “She did not discriminate between those in need - she reached out to all and tried to give them dignity.”
Former Beirut hostage Terry Waite paid tribute to Mother Teresa, saying she was a “remarkable lady”.
Mr Waite said: “She is leaving a legacy of totally dedicated compassion for the poor.”
Church leaders across the Midlands also expressed their sadness at the news.
Father James Ward, at The Sacred Heart Church in Eccleshall, met Mother Teresa both officially as a priest and accidentally while a student.
“I was hurrying through the concourse at Rome airport and I almost tumbled over her because she was so small,” he said.
“She was sitting on a suitcase. Some years later I met her in Birmingham when she came to the cathedral.
"I spoke to her and told her of that occasion at the airport. It was a lovely experience to meet her. She was a down-to-earth woman who had a word and a prayer in any circumstance.”
ens of thousands of people lined the route of Mother Teresa's funeral procession in Calcutta a week later.
Her successor as head of the Missionaries of Charity was Sister Nirmala.
In 1997,the order which Mother Teresa had run for almost half a century was 4,000-strong and established in 130 countries.
It cared for 7,000 children and treated about four million sick people each year.