Slot Loevestein (Loevestein Castle), or officially Museum Slot Loevestein, is one of the most well-known castles of the Netherlands. The castle was built by the knight Dirk Loef of Horne (hence "Loef's stein" (stone) house) between 1357 and 1368. Around 1575 it was expanded to a larger fortress surrounded by earthen fortifications with two (later three) stone bastions, two moats, an arsenal, and barracks for a commander and soldiers. The castle was also integrated into the Hollandic Water Line.

From 1614 on Slot Loevestein was used as a state prison. In 1619 a famous Dutch jurist, humanist, lawyer and poet “Hugo de Groot”, was imprisoned in the castle together with his wife and daughter to serve a life term sentence. In 1621 however he managed to escape from the castle by hiding in a big wooden bookcase, which was being brought out of the castle.

In the 19th century the castle was incorporated into a new and enlarged earthwork fortress, which made the castle an important stronghold in the New Dutch Waterline (a line of defensive works using water throughout the western part of Holland) and is part of this 200-kilometer long UNESCO World heritage Site. During all these works the bailey of the castle was torn down, the sole remnant is the round tower which was used as a powder magazine. Loevestein Castle lost its military function in 1952.

Nowadays Slot Loevestein is used as a medieval museum and function centre.