Burg Altmannstein, Medieval castle ruins in Altmannstein, Germany.

Burg Altmannstein is a castle ruin positioned on a hilltop near Altmannstein in Bavaria, Germany. The site displays remaining stone structures that offer views across the surrounding landscape.

Altmann II von Abensberg, a relative of the extinct Lords of Stein, had the castle built after 1232. In 1291 Duke Ludwig the Severe of Bavaria acquired it, and in 1446 Nuremberg troops captured it because its lord Johann von Abensberg harboured robber knights. The site has been a ruin since the late Middle Ages.

The ruins shape the character of Altmannstein and recall its role as a seat of an important noble family during medieval times. Visitors can observe remains that speak to a local past that defined life in the region for centuries.

The castle hill rises to 435 metres above sea level northeast of the market square. The site is protected by a section ditch on the inland side, and the 18-metre bergfried has its high entrance at 4.3 metres. The grounds are owned by the municipality of Altmannstein.

The castle was bought by Duke Ludwig the Strict of Bavaria in 1291. In 1446 Nuremberg troops captured it because its lord, Johann von Abensberg, had contacts with robber knights who were staying at the fortress. The late medieval Hungerturm, a prison tower, was linked to the town's fortifications by a surviving section of wall.