Eckartsau is a town in the district of Gänserndorf, in the Austrian state of Lower Austria. It lies in the eastern part of the country, within the federal province that surrounds Vienna.
The town is best known for Eckartsau Castle (Schloss Eckartsau), a former imperial hunting lodge and residence of the Habsburgs, which stands within the Danube-Auen National Park, a protected floodplain landscape along the Danube River. The castle and its surrounding parkland are among the area's principal points of interest.
Eckartsau's setting in the Marchfeld plain, close to the Danube wetlands, gives it a rural character typical of the Gänserndorf district. It is connected to neighbouring communities by regional roads and lies within reach of Vienna and the Slovak border region.