Founded around 1198, the Cistercian monastery in Osek, temporarily dissolved between 1580 and 1626, survived the Josephine secularizations, remaining an important religious center until 1950. After 1989, the abbey was renewed but today it lacks an active community. Its library holds about 680 manuscripts, including around 70 medieval ones. The medieval codices are now mostly kept in the National Library of the Czech Republic (as abbey's property), while others remain in Osek. Some manuscripts arrived from other Cistercian houses, while several original Osek volumes were dispersed elsewhere. About ten bear ownership marks such as Liber de Ossek, confirming their medieval origin. The library likely expanded mainly through donations, though study is limited by the lack of a modern manuscript catalogue.