Monastery of Santa Maria de Santes Creus (Catalan: Reial Monestir de Santa Maria de Santes Creus) is a Cistercian monastery in the municipality of Aiguamúrcia, Catalonia, Spain.
The monastery's origins date to 1158, when the Lords of Montagut y de Albá donated the village of Santes Creus to the monks of Valdaura. The papal decree that was required to establish a monastery was made by Pope Alexander II, and construction of the monastery began in 1174. The complex was completed in 1225.
King Peter III of Aragon chose to be buried in the Monastery of Santes Creus, as did his son James II (1276–1285) and his wife, Blanche of Anjou. James II had a section of the abbey turned royal rooms, the original Romanesque cloister rebuilt in the Gothic style of the 13th century, and a dome added to the church's crossing. The walls were built under King Peter IV. From the time of Peter IV, the royal favour was transferred to the Monastery of Poblet.
The monastic complex continued to expand during the 17th and 18th century, until, following the Ecclesiastical Confiscations of Mendizábal in 1835, the Cistercians left and building activities ceased. The monastery was declared a national monument in 1921.
The complex, built in accordance with Cistercian principles, included a church, a cloister, chapter house and dormitory. There were also a refectory, parlor, and scriptorium (writing hall). The complex is built in honey coloured stone, and the main buildings, including the church, have rooflines finished with crenellations.
The church, started in 1174, was finished around 1225. It was consecrated in 1211. It has a Latin cross plan, with a nave and lower aisles of six bays. The arms of the transept, which are the same width as the nave, each end in an apsidal chapel which is barely visible from the exterior. The chancel is rectangular, ending in the presbytery. The crossing is surmounted by a dome raised on a tall octagonal drum in Gothic style, and topped by a Baroque lantern.