The Royal, Celestial and Military Order of Our Lady of Mercy and the Redemption of the Captives, also known as Our Lady of Ransom (, abbreviated O. de M.) is a Roman Catholic mendicant order established in 1218 by St. Peter Nolasco in the city of Barcelona, at that time in the Principality of Catalonia (Crown of Aragon), for the redemption of Christian captives. Its members are most commonly known as Mercedarian friars or nuns. 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 for another who is in danger of losing their faith. The Order exists today in 17 countries.