Marschtorzwinger, Zwinger of the former town wall in Buxtehude, Germany

The Marschtorzwinger is a round zwinger of Buxtehude's former town wall, with a circular section 9.93 m across facing outward and a body tapering away from it. It has a ground floor with seven loopholes and an upper floor with nine, walls up to 1.90 m thick, and a pointed roof shown in a 1674 town view. A stone on the east side bears the town coat of arms and the number 1539.

Buxtehude's town wall was laid out in the 13th century and completed in the 14th. When firearms spread in the 15th and 16th centuries, massive round towers called Zwinger were built in front of its five corners. Dendrochronology of foundation timbers at the Linahzwinger dates those trees to 1551 and 1553, making a similar construction date around the mid-16th century likely for the Marschtorzwinger; a stone on its east side bears the town coat of arms and the number 1539. The adjoining Marschtor gate was demolished in the 19th century, and the tower was sold to a brewer for storage before the museum society bought it in 1914.

The Marschtorzwinger was sold to a brewer for storage in the mid-19th century, later passed to the Buxtehude museum society in 1914, and after its 1984–1986 restoration became a cultural centre for exhibitions and concerts. A stone on its east side bears the town coat of arms and the number 1539.

The Marschtorzwinger stands on the Westfleth in Buxtehude's old town, a short walk from the Buxtehuder Fleeth. It was fully restored between 1984 and 1986 using urban development funds, which gave it its present appearance. The round tower with its thick walls now serves as a cultural centre for exhibitions and concerts, so opening depends on the event programme.

A stone on the east side of the zwinger bears Buxtehude's town coat of arms and the number 1539, probably marking its construction year. The adjoining Marschtor gate was demolished in the 19th century, so the tower now stands free of the wall it once guarded.