Loket Castle (Czech: Hrad Loket) is a 12th-century Gothic style castle located about 12 km from Karlovy Vary on a massive rock in the town of Loket, Karlovarský kraj, Czech Republic. It is surrounded on three sides by the Ohře river. Once known as "the Impregnable Castle of Bohemia", because of its thick walls, it is one of the oldest and most valuable historical stone castles in the Czech lands. It is administered by the Loket Castle Foundation since 1993 and preserved today as a museum and national monument.