Burg Aschersleben, Medieval castle in Aschersleben, Germany.

Burg Aschersleben is a medieval castle situated on Wolfsberg hill, with surviving sections of defensive walls and a substantial tower still standing. The site now occupies grounds within the Aschersleben Zoo, where the historic structures form part of the visitor landscape.

The castle arose in the 11th or 12th century on the site of an early prehistoric refuge fort, and it is not the same as the lost ancestral castle of the Ballenstedt counts, later known as the Ascanians. In the 12th century it was destroyed during fighting between the Ascanians and Duke Henry the Lion. Its roughly 30-metre bergfried, originally a residential tower, later served Aschersleben as a watchtower; by the 13th century the site was already called a ruin.

The site is known as Altenburg or Alte Burg, and also as Ruine Askania. The tower ruin now serves as an enclosure for the zoo's eagle owls, and a small permanent exhibition in the animal keeper's house covers the castle's history.

Access to the castle is available through the zoo grounds, making it an interesting add-on to a zoo visit. The historic tower is visible from multiple vantage points and paths throughout the zoo area, allowing exploration at your own pace.

The tower ruin now serves as the enclosure for the zoo's eagle owls, and a small permanent exhibition in the animal keeper's house on the zoo grounds covers the castle's history. The site is also called Ruine Askania, and it is the only Aschersleben castle of which remains survive.