Burg Wasserburg, Medieval castle in Wasserburg am Inn, Germany.

Burg Wasserburg is a medieval castle positioned on a peninsula formed by the Inn River in Wasserburg am Inn. The complex features defensive walls, multiple structures spanning different periods, a chapel, and a Knights' Hall that visitors can explore.

The castle's early history is undocumented; a 13th-century charter now considered a forgery claims Count Engelbert of Attel moved his seat here in the mid-12th century. A predecessor of the castle chapel was mentioned in 1137. In 1247 Duke Louis II, the Strict, captured the castle and town after a 17-week siege, and Wasserburg became Wittelsbach property. Between 1529 and 1535 the castle was rebuilt as a Late Gothic palace with a monumental saddle roof and stepped gables.

The castle chapel, dedicated to St. Aegidius, was built in 1465 with a pointed-helmet tower; a predecessor chapel was mentioned in 1137. The name Wasserburg refers to the town and castle on the Inn loop, only seven-eighths surrounded by water. Today the former castle houses part of the surveying office and a senior home run by Maria Stern convent.

The castle stands on the highest point of the loop formed by the Inn, at Auf der Burg 3. The western Schanze, built in 1615, now serves as the main approach. Parts of the building house the surveying office and a senior home, so interior access is limited; the exterior walls and chapel tower can be viewed from the town below.

The castle sits on the highest point of a hill almost encircled by the Inn, with only about one eighth of the site bordered by land. Because of this, it is not a true water castle but rather a spur or ridge castle. Its position blocked the only land route to the town below.