Altes Zeughaus Wismar, Baroque military building in Wismar, Germany.

The Altes Zeughaus Wismar is a two-storey, nine-axis baroque plastered building on Ulmenstraße, built around 1700 with a hipped roof and a hanging truss in the roof structure. Each side has a portal with a rectangular frame; the street-side portal risalit was given pilasters, a triangular pediment and a coat of arms cartouche in 1869. Inside, a column-free ceiling construction creates a single hall measuring 15 by 60 metres, with 900 square metres of floor area.

A storm in 1699 caused a powder tower to explode, damaging the old armoury and much of Wismar, so a new building was needed. Around 1700, King Charles XII of Sweden had this two-storey arsenal built for the Swedish garrison; the plans are attributed to the Swedish fortification engineer Erik Dahlberg. In 1718 Wismar citizens bought it from the Swedes to use as a warehouse, and in 1754 it was sold to the city.

The name reflects its original purpose as a weapons storage facility, with the Swedish royal coat of arms still displayed above the entrance as a reminder of past rule.

The building now houses the Wismar city library. The upper floor was originally reached by an inclined ramp that allowed horses to haul heavy equipment; the courtyard and entrance area were redesigned in 2001/02 by landscape architect Jörn Wagner.

The upper floor was reached by an inclined ramp that let horses haul heavy equipment up. The roof frame uses a hanging truss, and the hall below covers 900 square metres, 15 by 60 metres, with no supporting pillars.