Plasy (ˈplasɪ) (Plass) is a small town in the Plzeň Region of the Czech Republic. It lies on the Střela River, some to the north from the region capital of Plzeň.
Plasy is also a Municipality with Commissioned Local Authority within the Kralovice Municipality with Extended Competence.
It is famous for its huge Cistercian monastery founded in 1144, which was rebuilt between 1661 and 1739 under the guidance of J. B. Mathey and J. B. Santini and became an important center of Baroque art. After Emperor Joseph II abolished nearly all religious orders in the Habsburg Empire, the monastery became the seat of the Princes of Metternich.
Today, the monastery is owned by the state and it is in a rather bad state though it is being slowly restored (and remains opened to public). There are also some regional archives placed there. No important industry is located in the town. With its scenic surroundings, the town is an important touristic center.