Burg Greifenstein is a castle in Lower Austria, Austria, overlooking the Danube. The castle was built probably in the 11th Century. It was first mentioned in 1135. At that time it already had a significant role in the defense system along the Danube. The owners of the castle changed frequently.
From the 16th century, the castle served primarily as a notorious prison of the ecclesiastical court. Throughout history, the castle was repeatedly invaded and damaged but repaired again and again. It was inhabited until about 1770, when it was abandoned and fell into disrepair. Until 1803 it belonged to the Bishops of Passau.