Kreva Castle (Belarusian: Крэўскі замак) is the ruins of a major fortified residence of Grand Dukes Gediminas and Algirdas in Kreva village, Belarus. Algirdas's brother Kęstutis was imprisoned and murdered in Kreva Castle in 1382. The Act of Krewo, the first step towards the Commonwealth of Poland-Lithuania, was signed in the castle three years later. The castle was sacked by the Crimean Tatars in the early 16th century and stood unoccupied for a long time. By the 19th century, much of the walls had crumbled away. The First World War dealt a final blow to the decaying structure, since the castle stood on the front line between Russian and German armed forces. In 19th and 20th centuries, the ruins were partially conserved, particularly by Poland in 1929. However the monument crumbles further.
In line with the recent reconstruction of other buildings and monuments in the region, the Smorgon District Executive Committee plan to restore parts of the castle. Although a complete restoration is impossible, they intend to rebuild main walls using fallen masonry, and to reconstruct the 'Big Tower' (also known as the Princely Tower, or the Tower of Kęstùtis). Survey work is to be carried out in 2013 and over 1 billion Belarus Roubles have been allocated for this purpose.