The Scapular of Our Lady of Mount Carmel (also known as the Brown Scapular) belongs to the habit of both the Carmelite Order and the Discalced Carmelite Order, both of which have Our Lady of Mount Carmel as their patroness. In its small form, it is widely popular among Catholics. Today, it serves as the prototype of all devotional scapulars. The liturgical feast day of Our Lady of Mount Carmel, July 16, is popularly associated with the devotion of the Scapular.

According to the Vatican's Congregation for Divine Worship, the Brown Scapular is "an external sign of the filial relationship established between the Blessed Virgin Mary, Mother and Queen of Mount Carmel, and the faithful who entrust themselves totally to her protection, who have recourse to her maternal intercession, who are mindful of the primacy of the spiritual life and the need for prayer."

In its origin as a practical garment, a scapular was a type of work apron, frequently used by monks, consisting of large pieces of cloth front and back joined over the shoulders with strips of cloth. It forms part of the habit of some religious orders including the Carmelites. The first Carmelite hermits who lived on Mount Carmel in the Holy Land in the 12th century are thought to have worn a belted tunic and striped mantle typical of pilgrims; when the Carmelites moved to Europe in the 13th century and became a mendicant order of friars they adopted a new habit that included a brown belted tunic, brown scapular, hood, and white mantle.

In the Middle Ages, a habit was an essential part of the identity of members of religious orders. To remove one's habit was tantamount to leaving the monastic state. The Carmelite Constitution of 1369 stipulates automatic excommunication for Carmelites who say Mass without a scapular, while the Constitutions of 1324 and 1294 consider it a serious fault to sleep without the scapular.

It was customary for laypeople who belonged to confraternities, sodalities, or third orders affiliated with the religious orders to wear some sign of membership, frequently some part derived from the religious habit such as a cord, cloak or scapular. During part of their history, the lay affiliates of the Carmelites wore the white mantle which the friars wore, or even the full habit. The small brown scapular and Mary's promise of salvation for the wearer, began to be promoted to the laity in the form we are familiar with today by Giovanni Battista Rossi, prior general of the Carmelites from 1564 to 1578.

The Carmelite scapular was widespread in European countries at the end of the 16th century. There are many books that include formulas of blessing for those who wear the scapular. The moment when they receive the scapular formally is significant, as is the hour of death.

According to traditional accounts, the Blessed Virgin Mary appeared at Cambridge to St. Simon Stock, a man not otherwise documented in historical record, but often described as a Prior General of the Carmelite Order in the middle of the 13th century. The legend states that the Virgin appeared to Stock, holding the Scapular, and promised that all who wear it will be spared suffering in Purgatory.

The first mention of the vision appeared almost 150 years after the date in 1251 when it is said to have occurred and is not noted in the earliest accounts of Simon Stock's life and miracles. The history of the Carmelite habit and legislation concerning it do not mention a tradition about the Blessed Virgin giving the Scapular to the Carmelites. Notable Carmelite writers of the 14th century do not mention the scapular. History even records an instance in 1375 when an English Carmelite named Nicholas Hornby engaged in a public debate with a Dominican friar in which Hornby ridiculed Dominican claims to have received their habit from the Blessed Virgin—this was a claim common to several different orders in the Middle Ages. Hornby showed no sign of being aware of any similar claim that had been made by a fellow English Carmelite in the preceding century.