Monasterio de Santa María de Sigena is a monastery in Villanueva de Sigena, Aragon, Spain. It was constructed between 1183 and 1208, by will of queen Sancha of Castile, wife of Alfonso II of Aragon, as a monastery for nuns from the richest families of Aragon.
The monastery flourished in the 14th century thanks to the royal support. In 1835, after state confiscations deprived of most of its revenues, it was abandoned by the nuns, although later some returned . In 1936, during the Spanish Civil War, it suffered a fire, and was restored in the 1950s. Starting from 1985, it is inhabited by nuns of the Sisterhood of Belén y de la Asunción de la Virgen.
The monastery church is on the Latin cross plan, with a single nave, a wide transept and three apse chapels. It is in Romanesque style, with elements from Cistercian and Mudéjar styles, such as the roofs. Notable is the main portal, featuring 14 archivolts.
The Romanesque cloister, once in ruins, owes its current appearance to a 1974 reconstruction. In 1936 the capitular hall's medieval paintings were moved the Museu Nacional d'Art de Catalunya in Barcelona.
Artworks include the royal tombs of Sancha and Peter of Castile; others, such as the painting walls, are in the National Museum of Art in Barcelona, while the former abbess' throne, in the Diocesan and Comarcal Museum of Lleida.