Loarre Castle is a fortress in Loarre, Spain. The complex was built largely during the 11th and 12th centuries, when its position on the frontier between Christian and Muslim lands gave it strategic importance. The first of the two major building programs began ca. 1020, when Sancho el Mayor (r. 1063–94) reconquered the surrounding lands from the Muslims. At least three towers, two of which survive, the Homage tower (Torre del Homenaje) and the "Tower of the Queen" (Torre de la Reina), as well as a chapel dedicated to Saint Mary of Valverde and connecting walls are attributed to this campaign. The Homage tower was built in an isolated position in front of the fortifications, to which it was connected by a wooden bridge. It contained a basement and five floors. The Torre de la Reina, comprising a basement and three floors, is particularly noteworthy for three sets of twin-arched windows, with columns of exaggerated entasis and trapezoidal capitals that have been related to both Lombard and Mozarabic architectural forms. The chapel is composed of a single-cell nave with an eastern apse covered by a semicircular vault. The original timber roof of the nave was replaced by a vault at the end of the 11th century.

After 1070, Loarre became increasingly important. In 1073, King Sancho installed a community of Augustinian canons, and it was from Loarre that he prepared for the conquest of Huesca in 1094. In 1097, however, his successor, Peter I of Aragon and Navarre, donated all the goods of Loarre to a new royal monastery at Montearagon. This evidence suggests that the second major construction program was undertaken between 1073 and 1097, and much building evidently does date from this period. By comparison with other monuments, however, it is also clear that the building and decorative program continued into the 12th century.