Queen of Heaven is a title given to the Blessed Virgin Mary by Christians mainly of the Roman Catholic Church, and also, to some extent, in Eastern Orthodoxy, to whom the title is a consequence of the First Council of Ephesus in the fifth century, in which the Virgin Mary was proclaimed "theotokos", a title rendered in Latin as Mater Dei, in English "Mother of God".
The Catholic teaching on this subject is expressed in the papal encyclical Ad Caeli Reginam, issued by Pope Pius XII. It states that Mary is called Queen of Heaven because her son, Jesus Christ, is the king of Israel and heavenly king of the universe; indeed, the Davidic tradition of Israel recognized the mother of the king as the Queen Mother of Israel. The Eastern Orthodox Churches do not share the Catholic dogma, but themselves have a rich liturgical history in honor of Mary.
The title Queen of Heaven has long been a Catholic tradition, included in prayers and devotional literature, and seen in Western art in the subject of the Coronation of the Virgin, from the High Middle Ages, long before it was given a formal definition status by the Church.
Queen of Heaven (Latin Regina Caeli) is one of many Queen titles used of the Virgin Mary. The title derived in part from the ancient Catholic teaching that Mary, at the end of her earthly life, was bodily and spiritually assumed into heaven, and that she is there honored as Queen.
Pius XII explained on the theological reasons for her title of Queen in a radio message to Fatima of May 13, 1946, Bendito seja:
He, the Son of God, reflects on His heavenly Mother the glory, the majesty and the dominion of His kingship, for, having been associated to the King of Martyrs in the ... work of human Redemption as Mother and cooperator, she remains forever associated to Him, with a practically unlimited power, in the distribution of the graces which flow from the Redemption. Jesus is King throughout all eternity by nature and by right of conquest: through Him, with Him, and subordinate to Him, Mary is Queen by grace, by divine relationship, by right of conquest, and by singular choice [of the Father].
According to Catholic doctrine, Mary was assumed into heaven and is with Jesus Christ, her divine Son and is represented in the Book of Revelation (chapter 11:19-12:6) as the woman clothed with the sun who gives birth to Christ.
In his 1954 encyclical Ad caeli reginam ("To the Queen of Heaven"), Pius XII points out that Mary deserves the title because she is Mother of God, because she is closely associated as the New Eve with Jesus' redemptive work, because of her preeminent perfection and because of her intercessory power. Ad caeli reginam states that the main principle on which the royal dignity of Mary rests is her Divine Motherhood... So with complete justice St. John Damascene could write: "When she became Mother of the Creator, she truly became Queen of every creature."