Central nave of the church Tomb of King Pedro I Tomb of Ines de Castro showing Christ presiding over the Last Judgement Royal Pantheon of the Alcobaça Monastery. The tomb in the foreground decorated with the Apostles belongs to Queen Urraca. Manueline vault and entrance to the sacristy Cloister and church of the Alcobasa Monastery Renaissance water basin within the Gothic fountain house in the cloister of the Monastery of Alcobasa

The Alcobaça Monastery is one of the first buildings associated with the Cistercian Order in Portugal. It was founded in 1153 as a gift from the first Portuguese king, Afonso I or Afonso Henriques (1112–1185), to Bernard of Clairvaux,[1] following the king's conquest of the city of Santarém from the Moors in March 1147. The foundation of the monastery was part of a larger strategy by King Afonso I to assert his authority and promote the colonisation of lands recently conquered from the Moors during the Reconquista.

Construction began in 1178, some 25 years after the first Cistercian monks settled in the Alcobaça region.[1] Initially, the monks lived in wooden houses and would only move to the newly built monastery in 1223. The church proper wasn't completed until 1252.[2] The church and the adjacent monastery are the earliest examples of truly Gothic architecture in Portugal and the church itself was the largest in Portugal at the time of its completion.[1] The final touch in this large medieval ensemble was given in the late 13th century, when King Denis I (1261–1325) ordered the construction of the Gothic cloister, also known as the Cloister of Silence.

The monks dedicated their lives to religious meditation, creating illuminated manuscripts in a scriptorium. The monks from the monastery produced an early authoritative history on Portugal in a series of books. The library at Alcobaça was one of the largest Portuguese medieval libraries, but was pillaged by the invading French in 1810, and many items were stolen in an anti-clerical riot in 1834, when the religious orders in Portugal were dissolved. The remnants of the monastery library, including hundreds of medieval manuscripts, are kept today in the Biblioteca Nacional de Portugal, Portugal's national library in Lisbon.

During the Middle Ages, the monastery quickly became a powerful and influential presence within the kingdom of Portugal. The monastery owned and developed extensive agriculture areas, and the abbot exerted influence over a large area. A public school was opened in 1269. The importance of the monastery can be measured by the fact that many monarchs were buried here in the 13th and 14th centuries. Kings Afonso II and Afonso III and their queens, Urraca of Castile and Beatrice of Castile, respectively, are buried here, as well as King Pedro I and his mistress, Inês de Castro, who was murdered on the orders of Pedro's father, King Afonso IV. After being crowned king, Pedro commissioned two magnificent Gothic tombs for himself and his mistress, both of which can still be seen inside the monastery church.[3]

During the reign of Manuel I, a second floor was added to the cloister and a new sacristy was built, following the characteristic Portuguese late Gothic style known as "Manueline". The monastery was further enlarged in the 18th century, with the addition of a new cloister and towers to the church, although the medieval structure was mostly preserved. In the Baroque period, the monks were famous for their clay sculptures, many of them are still inside the monastery. Elaborate tiles and altarpieces completed the decoration of the church.

The great 1755 Lisbon earthquake did not cause significant damage to the monastery, although part of the sacristy and some smaller buildings were destroyed. Far greater damage was caused by invading French troops in the first years of the 19th century during the Peninsular War, itself a part of the Napoleonic Wars. In addition to looting the library, they robbed the tombs and stole and burnt part of the inner decoration of the church. In 1834, with the dissolution of the monasteries in Portugal, the last monks left the monastery.

Alcobaça Monastery was classified as a National Monument on January 1, 1907, and included in the special protection zone on August 16, 1957.[4]