Maissau is a municipality in the district of Hollabrunn, in the Austrian state of Lower Austria. It lies in the Weinviertel region of northeastern Austria, north of the Danube and roughly 60 kilometres northwest of Vienna.
The town is best known for its historic castle, Schloss Maissau, which stands on a rocky outcrop above the settlement and has medieval origins. The surrounding countryside is characterised by vineyards, dry grassland and loess soils, part of a landscape noted for its rare flora and fauna.
Maissau is a small community with a long history; it was granted market rights in the Middle Ages and retains a compact historic centre with a parish church and remnants of its former town walls. It is connected by road and by the regional railway line serving the Hollabrunn district.