Lúcia was the youngest child of António dos Santos and Maria Rosa Ferreira (1869–1942),[2] both from Aljustrel, who married on 19 November 1890.

[1] Although peasants, the Santos family was not poor, owning land "in the direction of Montelo, Ortiga, Fátima, Valinhos, Cabeço, Charneca, and Cova da Iria.

But Father Cruz, a Jesuit missionary visiting from Lisbon, interviewed Lúcia after finding her in tears that day and concluded that "she understands what she's doing better than many of the others."

It left a deep impact on her: "I lost the taste and attraction for the things of the world, and only felt at home in some solitary place where, all alone, I could recall the delights of my First Communion.

[1] Between May and October 1917, Lúcia and her cousins Francisco and Jacinta Marto reported visions of a luminous lady, who they believed to be the Virgin Mary, in the Cova da Iria fields outside the hamlet of Aljustrel, near Fátima, Portugal.

Two of the secrets were revealed in 1941 in a document written by Lúcia, at the request of the Bishop of Leiria, José Alves Correia da Silva, partly to assist with the publication of a new edition of a book on Jacinta.

[10]: 199 When asked by Bishop da Silva in 1943 to reveal the third secret, Lúcia struggled for a short period, being "not yet convinced that God had clearly authorized her to act".

[10]: 203  She was under strict obedience in accordance with her Carmelite life, and conflicted as to whether she should obey her superiors, or the personal orders she believed were from Mary.

Witnesses present in the Cova da Iria that day, as well as some up to 25 miles (40 km) away,[13]: 192  reported that the Sun appeared to change colors and rotate, like a wheel of fire, casting off multicolored light across the landscape.

On 24 October 1925, she entered the Institute of the Sisters of St. Dorothy as a postulant in the convent in Pontevedra, Spain, just across the northern Portuguese border.

If one fulfilled the conditions on the First Saturday of five consecutive months, the Virgin Mary promised special graces at the hour of death.

Sister Lucia reported that on 13 June 1929, she had a vision during which the Blessed Virgin told her: "The moment has come in which God asks the Holy Father, in union with all the bishops of the world, to make the consecration of Russia to my Immaculate Heart, promising to save it by this means.

On 25 January 1938, a massive aurora borealis, described variously as "a curtain of fire" and a "huge blood-red beam of light", appeared in the skies over Europe and was visible as far away as Gibraltar and even parts of the United States.

[20] Lúcia believed this event was the "night illuminated by a strange light in the sky"[This quote needs a citation] which she had heard Mary speak about as part of the Second Secret, predicting the events which would lead to the Second World War and requesting Acts of Reparation including the First Saturday Devotions along with the Consecration of Russia.

She returned to Portugal in 1946 (where she visited Fátima incognito), and in March 1948, after receiving special papal permission, entered the Carmelite convent of Santa Teresa in Coimbra, where she resided until her death.

[7] On 13 February 2008 (the third anniversary of her death), Pope Benedict XVI announced that in the case of Sister Lúcia he would waive the five-year waiting period established by canon law before opening a cause for beatification.

[citation needed] Felipa Fernandes played her in The 13th Day, a straight-to-video feature film produced by Natasha Howes and directed by Dominic and Ian Higgins.

In the 2022 visual novel Anonymous;Code, The Holy Office 513, a powerful organisation within the catholic church, tries to create clones of Lùcia as well as Francisco and Jacinta Marto by planting their memories into artificial brains.