Mary Help of Christians (Latin: Sancta Maria Auxilium Christianorum; Spanish: Nuestra Señora María Auxiliadora de los Cristianos; Italian: Santa Maria Ausiliatrice) is a Roman Catholic Marian devotion, with a feast day inscribed into the General Roman Calendar on May 24.
Saint John Chrysostom was the first person to use this Marian title in year 345 as a devotion to the Virgin Mary. Don Bosco also propagated Marian devotion under this title. The title of Mary Help of Christians is associated with the defense of Christian Europe (Latin and Greek), the north of Africa and the Middle East from non-Christian peoples during the Middle Ages.
In 1572, during the expansion of the Islamic Ottoman Empire intended to invade Christian Europe, Pope Pius V invoked Christian armies and its victory achieved was consequently attributed to the intercession of Mary under this title. Ultimately, Pope Leo XIII granted a canonical coronation towards the Marian image bearing the same title on 17 May 1903, now permanently enshrined within the Basilica of Mary Help of Christians.
There are two inscriptions from the first centuries of Christianity in Greek related to the Virgin Mary: ? (Teotokos, Theotokos, Mother of God) and ? (Boetheia, the Helper). The Fathers of the Church referred to Mary as "?". John Chrysostom used the title in a homily of 345, Proclus in 476 and Sebas of Caesarea in 532. After the Patristic period (5th century), other persons used it like Romanos the Melodist in 518, the Patriarch of Jerusalem, Sophronius in 560, John of Damascus in 749 and Germanus I of Constantinople in 733.
In the view of Rev. Johann G. Roten, SM, the invocation of Mary as Help of Christians is part of the oldest prayer addressed directly to Mary, the Sub tuum praesidium, which was found on a papyrus dating, at the latest, from the end of the 3rd century. Praesidium is translated as "an assistance given in time of war by fresh troops in a strong manner."
Around 1576, Bernardino Cirillo, archpriest of Loreto, published at Macerata two litanies of the Blessed Virgin, which, he contended, were used at Loreto. One is in a form which is entirely different from our present text. Another form ("Aliae litaniae B.M.V.") is identical to the litany of Loreto approved by Pope Clement VIII in 1601 and now used throughout the entire Church. This second form contains the invocation Auxilium Christianorum. Possibly warriors returning from the Battle of Lepanto (7 October 1571) visited the sanctuary of Loreto, and saluted the Holy Virgin there for the first time with this new title. It is more probable, however, that it is only a variation of the older invocation Advocata Christianorum, found in a litany of 1524.
Torsellini (1597) and the Roman Breviary (May 24, Appendix) say that Pope Pius V inserted the invocation in the litany of Loreto after the battle of Lepanto. But the form of the litany in which it is first found was unknown at Rome at the time of Pius V.
The feast of Our Lady, Help of Christians, was instituted by Pope Pius VII. By order of Napoleon I of France, Pope Pius VII was arrested on 5 June 1808, and detained a prisoner first at Grenoble, and then at Fontainebleau. In January 1814, after the battle of Leipzig, he was brought back to Savona and set free on 17 March, on the eve of the feast of Our Lady of Mercy, the Patroness of Savona. The journey to Rome was a veritable triumphal march. The pontiff, attributing the victory of the Church after so much agony and distress to the Blessed Virgin, visited many of her sanctuaries on the way and crowned her images (e.g., the "Madonna del Monte" at Cesena, "della Misericordia" at Treja, "della Colonne" and "della Tempestà" at Tolentino). The people crowded the streets to catch a glimpse of the venerable pontiff who had so bravely withstood the threats of Napoleon. He entered Rome on 24 May 1814, and was enthusiastically welcomed. To commemorate his own sufferings and those of the Church during his exile Pope Pius VII extended the feast of the Seven Dolours of Mary to the universal Church on 18 September, 1814.
When Napoleon left Elba and returned to Paris, Murat was about to march through the Papal States from Naples; Pius VII fled to Savona 22 March 1815. After the Congress of Vienna and the battle of Waterloo, the pope returned to Rome on 7 July 1815. To give thanks to God and Our Lady, on 15 September 1815 he declared 24 May, the anniversary of his first return, to be henceforth the feast of Our Lady, Help of Christians. The 1913 Catholic Encyclopaedia article commented that "it has spread nearly over the entire Latin Church, but is not contained in the universal calendar."
The Marian feast has been celebrated by the order of Servites since the 17th century. The veneration to Mary became popular under this title in Rome especially, where the feast was especially promoted by Saint John Bosco and Saint Vincent Pallotti Saint John Bosco was an ardent promoter of devotion to "Mary, Help of Christians". He even built a huge basilica in her honour in 1868 and founded a religious congregation for women, under the title of, "The Daughters of Mary, Help of Christians". Interpreting the painting he had commissioned inside the basilica, St. John Bosco referred to it as depicting Mary Mother of the Church. This suggests an identical connection to the way in which popes have addressed Mary as both Mother and Help of the Church. Recall the two Marian Greek attribution of (Teotokos, Theotokos, Mother of God) and ? (Boetheia, the Helper) at the start of this article? St. John Bosco in fact, chose this devotion because of its affinity to his devotion to the Church, the bearer of Christ.
Vatican II, in the Constitution on the Church (sections 61, 62), cites this title of Mary, placing it in the context of Mary's maternal role. "In an utterly singular way she co-operated by her obedience, faith, hope and burning charity in the Saviour's work of restoring supernatural life to souls. For this reason she is a mother to us in the order of grace...By her maternal charity, Mary cares for the brethren of her Son who still wander through this world in the midst of dangers and difficulties until they are led to the happiness of their heavenly home".
The Church has traditionally focused on two aspects of Our Lady's help on this feast day. Firstly, the Church focuses in this feast on the role of Our Lady's intercession in the fight against sin in the life of a believer. Secondly, the Church focuses on Our Lady as one who assists Christians as a community, through her intercession, in fighting against anti-Christian forces.
Michael Daniel observes that, while this approach may be regarded as outdated, in light of Vatican II, where the world and non-Christians elements therein were seen in a positive rather than a hostile or threatening light, it would seem that it would be naïve on the part of Christians to regard all movements and all social trends as either good or harmless.
It became the patronal feast of Australasia, a double of the first class with an octave. After the reforms of the Second Vatican Council, it was designated a solemnity to be kept on the first available Sunday on or after 24 May.
The Fathers of the Foreign Missions of Paris, in accordance with a vow (1891), celebrated this feast with great splendor in their churches.
It has attained special renown since Don Bosco, founder of the Salesian Congregation, dedicated his foundation to Our Lady, Help of Christians, the mother church of his congregation at Turin on 9 June 1868. The Salesians have carried the devotion to their numerous establishments.
It was established due to the great appreciation of Saint Don Bosco for this Marian title and the development of the Salesian works in many countries since the second half of the 19th century. Although it is commonly associated with the Roman Catholic Church, the Orthodox Church has also known the devotion since 1030 in Ukraine, when the country was defended from a barbarian invasion.
The Salesian National Shrine of Our Lady Help of Christians is located in Stony Point, New York. There is also the National Shrine of Mary Help of Christians in Parañaque City, Philippines, which is also in the care of the Salesians of Don Bosco 
The Abbey of Mary Help of Christians, better known as Belmont Abbey, is a small American monastery of Benedictine monks in the town of Belmont, Gaston County, North Carolina, outside of Charlotte, North Carolina. The minor basilica of Our Lady Help of Christians is listed on the National Register of Historic Places.
There is a chapel of Our Lady Help of Christians at the Basilica of the Immaculate Conception in Washington D.C.
Under this title, the Virgin Mary is venerated by many Chinese Catholics, particularly at the Shrine of our Lady of Sheshan. In May 2007, Pope Benedict XVI designated 24 May her feast for the Roman Catholics in China, who face persecution and restriction from the Chinese Patriotic Catholic Association.
Altar at Mariahilf church Vienna