(from Latin rosarium, “rose garden”), religious exercise in which prayers are recited and counted on a string of beads or a knotted cord. By extension, the beads or cord may also be called a rosary. The practice is widespread, occurring in virtually every major religious tradition in the world.

In Christianity the practice was adopted in the 3rd century by Eastern Christian monks, and various forms of the rosary were developed. In Roman Catholicism the rosary became a popular method of public and private prayer. The most common rosary is the one devoted to Mary, the Rosary of the Blessed Virgin, the prayers of which are recited with the aid of a chaplet, or rosary. The beads of the chaplet are arranged in five decades (sets of 10), each decade separated from the next by a larger bead. The two ends of the chaplet are joined by a small string holding a crucifix, two large beads, and three small beads.

Traditionally, the Rosary of the Blessed Virgin requires three turns around the chaplet. It consists of the recitation of 15 decades of Hail Marys (Hail Mary) (150 Hail Marys), each one said while holding a small bead. On the larger beads separating the decades, different prayers are said (the Gloria Patri and the Our Father (Lord's Prayer)) and particular mysteries are meditated upon. The 15 mysteries are events from the life, death, and glorification of Jesus Christ and Mary; they are divided into three sets of five—the joyous, the sorrowful, and the glorious mysteries. The introductory and concluding prayers of the rosary vary.

In 2002 Pope John Paul II added a fourth set of mysteries, the “luminous mysteries,” or mysteries of light. The five new mysteries celebrate events in Jesus' ministry, including his baptism; his miracle at Cana, where he turned water into wine; his proclamation of the kingdom of God; the Transfiguration, in which he revealed his divinity to three of his Apostles; and his establishment of the Eucharist at the Last Supper.

The origin of the Rosary of the Blessed Virgin is not certain, though it has been associated with St. Dominic (Dominic, Saint), founder of the Dominican order in the early 13th century. The devotion probably developed gradually as a substitute for the recitation of the psalms or for the divine office sung by monks at the various canonical hours each day. It reached its definitive form in the 15th century through the preaching of the Dominican Alan de la Roche and his associates, who organized Rosary Confraternities at Douai in France and at Cologne. In 1520 Pope Leo X gave the rosary official approbation, and it has been repeatedly commended by the Roman Catholic church. Since the 1960s, however, public recitation of the rosary has become less frequent. John Paul II's addition of new mysteries, which are not required for reciting the rosary, was intended to revive interest in the practice; some traditional Catholics, however, have rejected the new mysteries, believing that they upset the relationship between the original number of mysteries and their corresponding psalms.

In Eastern Orthodoxy the prayer rope predates the Catholic rosary and is mainly a monastic devotion. Rosaries of 33, 100, or 300 knots or beads are the common sizes, and they are used to count repetitions of the Prayer of the Heart (Jesus prayer) (the Jesus Prayer). The Russian Orthodox (Russian Orthodox church) vertitza (“string”), chotki (“chaplet”), or lievstoka (“ladder”) is made of 103 beads, separated into irregular sections by 4 large beads and joined together so that the lines of beads run parallel, thus suggesting the form of a ladder; the parallel lines symbolize the ladder seen by Jacob in his dream and remind the faithful of the spiritual climb toward greater devotion and virtue. In the Romanian church the chaplet is called matanie (“reverence”) because the monk makes a profound bow at the beginning and end of each prayer counted on the beads.

The Anglican (Anglicanism) Prayer Beads are a blend of the Orthodox and the Catholic rosaries. They have four sections (“weeks”) of seven beads each, four larger “cruciform” beads separating each week, and an invitatory bead and a cross at the base. A prayer is said first on the cross and then on each of the 33 beads—33, according to tradition, equaling the number of years in Jesus' earthly life—and the “circle of prayers” is typically performed three times (symbolic of the Trinity), making the total number of prayers 100, which represents the fullness of creation.

In Islam (Islām) the rosary (subḥa (subḥah)) consists of three groups of beads whose total is also 100. Each bead represents one of the “most beautiful names of God,” and the rosary serves to count these names. The rosary is also used in an act of prayer and is carried by all classes of Muslims, especially pilgrims.