The Rosary (; Latin: rosarium, in the sense of "crown of roses" or "garland of roses"), also known as the Dominican Rosary, refers to a set of prayers used primarily in the Catholic Church, and to the physical string of knots or beads used to count the component prayers. When referring to the prayer, the word is usually capitalized ("the Rosary", as is customary for other names of prayers, such as "the Lord's Prayer", and "the Hail Mary"); when referring to the prayer beads as an object, it is written with a lower-case initial letter (e.g. "a rosary bead").

The prayers that compose the Rosary are arranged in sets of ten Hail Marys, called "decades". Each decade is preceded by one Lord's Prayer ("Our Father"), and traditionally followed by one Glory Be. Some Catholics also recite the "O my Jesus" prayer after the Glory Be; it is the best-known of the seven Fátima prayers that appeared in the early 20th century. Rosary prayer beads are an aid for saying these prayers in their proper sequence.

Usually, five decades are recited in a session. Each decade provides an opportunity to meditate on one of the Mysteries of the Rosary, which recall events in the lives of Jesus Christ and his mother Mary.

In the 16th century Pope Pius V established a standard 15 Mysteries of the Rosary, based on long-standing custom. This groups the mysteries in three sets: the Joyful Mysteries, the Sorrowful Mysteries, and the Glorious Mysteries. In 2002, Pope John Paul II said it is fitting that a new set of five be added, termed the Luminous Mysteries, bringing the total number of mysteries to 20. The mysteries are prayed on specific days of the week; with the addition of the Luminous Mysteries on Thursday, the others are the Glorious on Sunday and Wednesday, the Joyful on Monday and Saturday, and the Sorrowful on Tuesday and Friday.

Over more than four centuries, several popes have promoted the Rosary as part of the veneration of Mary in the Catholic Church, and consisting essentially in meditation on the life of Christ. The rosary also represents the Catholic emphasis on "participation in the life of Mary, whose focus was Christ", and the Mariological theme "to Christ through Mary".