Pius XII established this feast in 1954. But Mary’s queenship has roots in Scripture. At the Annunciation, Gabriel announced that Mary’s Son would receive the throne of David and rule forever. At the Visitation,
Elizabeth calls Mary
“mother of my Lord.” As in all the mysteries of Mary’s life, Mary is closely
associated with Jesus: Her queenship is a share in Jesus’ kingship. We can also
recall that in the Old Testament the mother of the king has great influence in
In the fourth century St. Ephrem (June 9) called Mary “Lady” and “Queen.” Later Church fathers and doctors continued to use the title. Hymns of the 11th to 13th centuries address Mary as queen: “Hail, Holy Queen,” “Hail, Queen of Heaven,” “Queen of Heaven.” The Dominican rosary and the Franciscan crown as well as numerous invocations in Mary’s litany celebrate her queenship.
Above from: American Catholic - Queenship of Mary