October is designated by the Catholic Church as the "Month of the Rosary" because in this month the Church celebrates the Marian advocation of "Our Lady of the Rosary" on Oct. 7.   

The feast of Our Lady of the Rosary, also celebrated as Our Lady of Victory or Victories, was established by Pope St. Pius V in 1571 to celebrate the miraculous victory of the Christian forces in the Battle of Lepanto on Oct. 7 of that year. Previous to the decisive battle, St. Pius V had requested all Western Christians to pray the rosary; thus he attributed the victory to the power of the Marian prayer rather than the power of ships and cannons.

Two years before establishing the feast, in 1569, Pope St. Pius V officially approved the rosary in its present form with the papal bull Consueverunt Romani Pontifices ("The Roman Pontiffs are accustomed," the first words of the document). In a development from earlier methods of praying the rosary, the new version included the second half of the Hail Mary, as well as the “Glory Be” prayer at the end of each mystery.