The military Order of Mountjoy (Sp. Montegaudio) was most probably established in 1173 by a Galician nobleman named Rodrigo Alvarez de Sarria and transferred to Aragon (Alfambra) shortly thereafter.
Rodrigo had professed in the Order of Santiago, but was allowed to found an order of stricter observance by the papal legate, Cardinal Hyacinth (later pope as Celestine III). From the 1170s the brethren followed a modified form of Cistercian observance, and the order, its possessions, and its denomination (after the site of Mons Gaudii close to Jerusalem) were confirmed by Pope Alexander III in May of 1180. The order was particularly fostered by King Alfonso II of Aragon, who hoped to gain assistance in securing recently conquered areas in southern Aragon. From 1177 the institution’s spiritual center was considered to be in the Holy Land, where it received donations from King Baldwin IV of Jerusalem and other magnates. The order also acquired assets in Italy, but despite its title, its economic and administrative headquarters always remained on the Iberian Peninsula, particularly in Aragon. After its founder’s death (probably in 1188), the order was amalgamated with the redemptionist Hospital of the Holy Redeemer of Teruel and henceforth committed itself to devoting a quarter of its revenues to the redemption of Christian captives. The brethren’s Aragonese possessions were incorporated by the Templars in 1196, while a dissident group led by Rodrigo Gonzalez established itself in the castle of Montfragüe (Monsfrag) on the river Tagus. It was known as the Order of Montfragüe, and was ultimately amalgamated with the Order of Calatrava in 1221.