The Royal, Celestial and Military Order of Our Lady of Mercy and the Redemption of the Captives (Latin: Ordo Beatae Mariae de Mercede Redemptionis Captivorum, abbreviated O. de M.), also known as the Mercedarians, is a Catholic mendicant order established in 1218 by Peter Nolasco in the city of Barcelona, at that time the capital of the Principality of Catalonia, part of the Crown of Aragon, for the redemption of Christian captives.

One of the distinguishing marks of the Order of the Blessed Virgin Mary of Mercy is that, since its foundation, its members are required to take a fourth vow: to die, if necessary, for another who is in danger of losing their faith.

In the lands of Visigothic Spain, both Christian and Muslim societies had become accustomed to the buying and selling of captives, so much so that tenth-century Andalusian merchants formed caravans to purchase slaves in Eastern Europe.

Biographers agree that, at some point in his youth, Nolasco became concerned with the plight of Christians captured in Moorish raids and that he decided to establish a religious order to succor these unfortunates.

From the year 1192 certain noblemen of Barcelona had formed a confraternity for the purpose of caring for the sick in hospitals, and also for rescuing Christian captives from the Moors.

Tradition has it that around 1218, Nolasco and King James I of Aragon each experienced separately a vision of the Virgin Mary, who asked them to found a religious order dedicated to rescuing the many Christian captives held by the Muslims.

[10] Nolasco's confessor, Raymond of Penyafort, a Dominican friar and former canon of Barcelona, encouraged and assisted him in this project; and King James also extended his protection.

On August 12, 1230, Maimó Gombal, a resident of Barcelona and a man of some property, directed in his will that 100 Papal States scudi be handed over to Nolasco for the ransoming of captives.

Here special circumstances associated with the frontier —an abundance of new land awaiting Christian settlement and an arena for the practice of charitable ransoming— created an ideal environment for the new Order.

While evidence is scant, one has to assume that this support came in recognition of the Order's work in ransoming captives in a war zone that remained quite active.

James I, whose descendants claimed him to be the Mercedarian founder, had in fact no documented contact with the Order until the late 1230s and early 1240s, at which time he granted formerly Muslim lands in Valencia, especially the Shrine of Santa Maria del Puig, patron saint of the kingdom.

In the 15th century, a movement grew up among the monasteries of the Order seeking a stricter lifestyle, keeping more exactly the Rule of St. Augustine under which the friars live.

As a result of the Counter-Reformation, spurred by the Council of Trent (1545-1563), this goal was revived and further developed by Friar John Baptist of the Blessed Sacrament (Spanish: Juan Bautista del Santísimo Sacramento).

[16] Eventually a feast day was instituted and observed on September 24, first in the religious order, then in Spain and France, and on February 22, 1696 Pope Innocent XII extended it to the entire church.

The Mercedarians keep this day as a first class feast, with a vigil, privileged Octave and Proper Office under the title: Solemnitas Descensionis B. Mariæ V. de Mercede.

In the Philippines, the oldest known center of devotion to Our Lady of Mercy is in Bahay Pare, Candaba, Pampanga, whom they call "Nuestra" or "Apung de la Merced".

Devotees flock to the parish to ask Mary to intercede for their spiritual, mental, and physical health, for their families and studies, and for the increase of vocations to the priesthood and consecrated life.