The consecration of Russia to the Immaculate Heart of Mary by a reigning pope was requested during a Marian apparition by Our Lady of Fátima on 13 July 1917, according to Lúcia dos Santos (Sister Lúcia), one of the three visionaries who claimed to have seen the apparition. Sister Lucia said that at different times the Blessed Virgin Mary had given her a message of promise that the consecration of Russia to the Immaculate Heart of Mary would usher in a period of world peace.

Popes Pius XII, Paul VI and John Paul II all consecrated Russia to the Immaculate Heart of Mary, although without specifically referencing Russia or the USSR. On March 25, 2022, Pope Francis consecrated Russia to the Immaculate Heart of Mary, alongside Ukraine, with both countries mentioned for the first time. This occurred during the Russian invasion of Ukraine.

According to Sister Lúcia, the Virgin Mary requested the consecration of Russia to her Immaculate Heart both at Fatima in 1917 and, later, more explicitly at Pontevedra in 1929.

In two letters she sent in May 1930 to Father Gonçalves, her confessor, Sister Lúcia linked the consecration of Russia with the Devotion of the Five First Saturdays, which she had first discussed in context of the apparitions she had purportedly experienced previously as a postulant at Pontevedra in 1925. The Church has issued no decision regarding the reported visions at Pontevedra. In August 1941, Sister Lúcia wrote her memoir in which she described the apparition of 13 July 1917. She said that the Blessed Virgin Mary told them:

"God wishes to establish in the world devotion to my Immaculate Heart. If what I say to you is done, many souls will be saved and there will be peace. The [First World] war is going to end; if people do not cease offending God, a worse one will break out during the pontificate of Pius XI. When you see a night illumined by an unknown light, know that this is the great sign given you by God that He is about to punish the world for its crimes, by means of war, famine, and persecutions of the Church and of the Holy Father. To prevent this, I shall come to ask for the consecration of Russia to my Immaculate Heart, and the communion of reparation on the first Saturdays. If my requests are heeded, Russia will be converted, and there will be peace. If not, she will spread her errors throughout the world, causing wars and persecutions of the Church. The good will be martyred, the Holy Father will have much to suffer, various nations will be annihilated. In the end, my Immaculate Heart will triumph. The Holy Father will consecrate Russia to me, and she will be converted, and a period of peace will be granted to the world."

Some Catholics who support the position of the Catholic Church claim that the apparitions at Fátima took place after the February Revolution of 1917 that deposed Tsar Nicholas II from power and the April 16 return of Vladimir Lenin to Russia.

The alleged message given by the Virgin Mary at Fatima is considered a private revelation.

The teaching of the Roman Catholic Church distinguishes between "public Revelation" and "private revelations". The term "public Revelation" finds its literary expression in the Bible and "reached its fulfilment in the life, death and resurrection of Jesus Christ". In this regard, Catechism of the Catholic Church quotes John of the Cross: