The last surviving witness to whom the Virgin Mary is said to have appeared in a series of apparitions in Portugal in 1917 has died aged 97.
The Pope believed the Virgin Mary of Fatima helped save his life
Sister Lucia de Jesus dos Santos died at the convent where she had been living since the 1940s, the Roman Catholic Church said.
She was one of three shepherd children who claimed they spoke to the Virgin Mary near Fatima town over six months.
The apparitions turned Fatima into one of Catholicism's most revered sites.
The Virgin Mary is said to have revealed prophecies of key 20th Century events, including the end of World War I, the start of World War II and the rise and fall of Soviet communism.
The Church believes the third "secret", not unveiled until 2000, foretold the attempted assassination of Pope John Paul on 13 May 1981, the anniversary of one of the 1917 apparitions.
The Church announced that Sister Lucia died at her Carmelite convent at Coimbra in central Portugal on Sunday.
"She had been weak for several weeks and had not left her cell," said Coimbra Bishop Albino Cleto.
Her body is due to be laid out in Coimbra's cathedral before her funeral on Wednesday.
Sister Lucia was just 10 when she and her two younger cousins, Francisco Marto and his sister Jacinta, are said to have seen the Virgin Mary above an olive tree near the central town of Fatima.
She was the only one who claimed to have heard clearly what the Virgin Mary said.
While her cousins both died within three years of the apparitions ending, during the flu pandemic, Sister Lucia went on to write down what she had been told.
The cousins were tending sheep when they saw the visions
The first two parts of the prophecy were known for decades and interpreted as predicting the world wars.
But the third prophecy was kept secret and sparked much speculation about its content.
When the Vatican revealed its interpretation of the vision, the Pope credited the Madonna of Fatima with his survival following the 1981 attempt on his life by Turkish gunman Mehmet Ali Agca in St Peter's Square.
The Pope made several visits to Fatima - along with pilgrims from all over the world - and first met Sister Lucia during a trip in 1991.
He travelled to Fatima in 2000 to beatify Francisco and Jacinta, and steps are expected to be taken to beatify Sister Lucia as well.