Monastery in Klášter Hradiště nad Jizerou, Medieval Cistercian monastery in Mladá Boleslav District, Czech Republic.

The Cistercian abbey of Klášter Hradiště nad Jizerou stands on a hill above the Jizera and Zábrdka confluence, unusual for a Cistercian site. Its church measured 75 m by 40 m; the surviving north portal of the transept, carved with plant ornament around 1260, and parts of the choir walls remain, while a 1560 parish church and the brewery buildings occupy the rest.

The Cistercian abbey was founded in 1145 or 1177, both dates given in the Plasy chronicle Tilia Plassensis, probably by the Markvartice family; an abbot Thidricus is documented in 1184. Around 1400 it held 112 villages and farms, and in 1404–1405 Jan Hus sat on a commission investigating monks who staged fake miracles. On 30 April 1420 the Orebitess burned it and it was never renewed.

The name Hradiště appears in records as Grandis, Gradisch and Hradisch before 1351, when it became Gredis Monachorum, source of the town name Mnichovo Hradiště. The monastery took its name from the locality, and its convent was settled from Plasy.

The grounds sit on a hill above the Jizera and Zábrdka confluence, with the former convent church's north portal and surviving masonry best reached from the village side. The site is now occupied by the Klášter brewery, so access to the historic remains depends on the brewery grounds rather than a separate monument entrance.

The brewery founded here in 1852 still operates under the name Pivovar Klášter, so brewing never stopped. The Waldstein-Wartenberg family converted the whole complex, and extensive cellars were dug beneath it over time.