On 11 February 1858, Bernadette Soubirous went with her sisters Toinette and Jeanne Abadie to collect some firewood and bones in order to buy some bread. After taking off her shoes and stockings to wade through the water near the Grotto of Massabielle, she said she heard the sound of two gusts of wind (coups de vent) but the trees and bushes nearby did not move. A wild rose in a natural niche in the grotto, however, did move. From the niche, or rather the dark alcove behind it, "came a dazzling light, and a white figure." She was dressed all in white, apart from the blue belt fastened around her waist and the golden yellow roses, one on each foot, the colour of her rosary. Bernadette tried to keep this a secret, but Toinette told her mother. After parental cross-examination, she and her sister received corporal punishment for their story.

Three days later, Bernadette returned to the Grotto. She had brought holy water as a test that the apparition was not of evil provenance, and demanded that if she were from God, she must stay, but if she were evil, she must go away; however, she said the vision only inclined her head gratefully when the water was cast and she made her demands.

Bernadette's companions are said to have become afraid when they saw her in ecstasy. She remained ecstatic even as they returned to the village. On 18 February, she spoke of being told by the Lady to return to the Grotto over a period of two weeks. She quoted the apparition: I promise to make you happy, not in this world, but in the next.

After that the news spread and her parents took interest. Bernadette was ordered by her parents to never go there again. It was a shock when people heard her story as it was so unlikely. She went anyway, and on 24 February, Bernadette related that the apparition asked for prayer and penitence for the conversion of sinners. The next day, she said the apparition asked her to dig in the ground and drink from the spring she found there. This made her disheveled and some of her supporters were dismayed, but this act revealed the stream that soon became a focal point for pilgrimages.

Although it was muddy at first, the stream became increasingly clean. As word spread, this water was given to medical patients of all kinds, and many reports of miraculous cures followed. Seven of these cures were confirmed as lacking any medical explanations by Professor Verges in 1860. The first person with a “certified miracle” was a woman whose right hand had been deformed as a consequence of an accident. Several miracles turned out to be short-term improvement or even hoaxes, and Church and government officials became increasingly concerned. The government fenced off the Grotto and issued stiff penalties for anybody trying to get near the off-limits area. In the process, Lourdes became a national issue in France, resulting in the intervention of emperor Napoleon III with an order to reopen the grotto on 4 October 1858. The Church had decided to stay away from the controversy altogether.

Bernadette, knowing the local area well, managed to visit the barricaded grotto under cover of darkness. There, on 25 March, she said she was told: "I am the Immaculate Conception" ("que soy era immaculada concepciou"). On Easter Sunday, 7 April, her examining doctor stated that Bernadette, in ecstasy, was observed to have held her hands over a lit candle without sustaining harm. On 16 July, Bernadette went for the last time to the Grotto. I have never seen her so beautiful before, she reported.

The Church, faced with nationwide questions, decided to institute an investigative commission on 17 November 1858. On 18 January 1860, the local bishop finally declared that: The Virgin Mary did appear indeed to Bernadette Soubirous. These events established the Marian veneration in Lourdes, which together with Fátima, is one of the most frequented Marian shrines in the world, and to which between 4 and 6 million pilgrims travel annually.

In 1873 the great "national" French pilgrimages were inaugurated. Three years later the basilica was consecrated and the statue solemnly crowned. Pope Leo XIII authorized a special office and a Mass, in commemoration of the apparition, and in 1907 Pius X extended the observance of this feast to the entire Church; it is now observed on 11 February.