Alter Wasserturm, Water tower in Wismar, Germany.

The Alter Wasserturm is a stone defensive tower on Wismar's former city wall, converted into a water tower in 1685 by Jochen von Schwoll for mayor Anton Scheffel. A horse-driven Göpelwerk pumped water into a tank at the top. It is the last stone witness of the city's fortifications besides the Wassertor and small remains of the wall.

The tower was originally a defensive tower of Wismar's medieval fortifications. In 1685, after the Danish occupation of 1675–1680 exposed a weak point in the city's water supply, mayor Anton Scheffel commissioned the Lübeck builder Jochen von Schwoll to convert it into a water tower, pumping water by horse-driven Göpel into a tank at the top. In 1715 it was linked by wooden pipes to the Wasserkunst on the market square, a system that worked until 1873.

The name Alter Wasserturm (Old Water Tower) survives although the tower stopped serving as a water tower in 1873, when more efficient supply systems made it redundant. Its conversion in 1685 was ordered by mayor Anton Scheffel, who entrusted the Lübeck builder Jochen von Schwoll with the work; a horse-driven Göpel pump lifted water into a tank at the top of the tower.

The tower stands by the former city wall, near the historic Wassertor at Wismar's harbour; the surviving fragments of the medieval wall are close by. It is a short walk from the old town and the market square, where the Wasserkunst once fed the same wooden pipes. The tower itself is not open as a viewing platform.

The tower shows a rare combination of defensive function and water storage within a single building, making it a notable example of dual-purpose design. This double function remains visible today in its construction, with older and newer building elements still clearly distinguishable.