Cistercian architecture is a style of architecture associated with the churches, monasteries and abbeys of the Roman Catholic Cistercian Order. It was headed by Abbot Bernard of Clairvaux (d. 1153), who believed that churches should avoid superfluous ornamentation so as not to distract from the religious life. Cistercian architecture was simple and utilitarian. Although images of religious subjects were allowed in very limited instances, such as the crucifix, many of the more elaborate figures that commonly adorned medieval churches were not. Their capacity for distracting monks was criticised in a famous letter by Bernard. Early Cistercian architecture shows a transition between Romanesque and Gothic architecture. Later abbeys were also constructed in Renaissance and Baroque styles, though by then simplicity is rather less evident.
In terms of construction, buildings were made where possible of smooth, pale, stone. Columns, pillars and windows fell at the same base level, and if plastering was done at all, it was kept extremely simple. The sanctuary kept a simple style of proportion of 1:2 at both elevation and floor levels. To maintain the appearance of ecclesiastical buildings, Cistercian sites were constructed in a pure, rational style; and may be counted among the most beautiful relics of the Middle Ages.
Most Cistercian abbeys and churches were built in remote valleys far from cities and populated areas, and this isolation and need for self-sustainability bred an innovativeness among the Cistercians. Many Cistercian establishments display early examples of hydraulic engineering and waterwheels. After stone, the two most important building materials were wood and metal. The Cistercians were careful in the management and conservation of their forests; they were also skilled metallurgists, and their skill with metal has been associated directly with the development of Cistercian architecture, and the spread of Gothic architecture as a whole.