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 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 Mary, mother of Jesus. 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.
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 .