Donaustauf Castle (German: Burgruine Donaustauf) is a ruined hill castle located at a height of 424 m above sea level (NN) on a hill spur overlooking the River Danube by the market village of Donaustauf in the Upper Palatine county of Regensburg in the south German state of Bavaria.

Donaustauf grew up during the Middle Ages under the protection of the mighty fortifications of the castle.

The castle is built on the site of a Celtic fort of unknown size and importance dating to around 500 BC.

Based on excavations in 1981 of the northeast side of the lower outer bailey it appears to date to the late Hallstatt period.

Between 914 and 930 AD, Bishop Tuto of Regensburg had a castle built here to defend the area from Hungarian invasion.