The Spačva basin (Serbo-Croatian: Spačvanski bazen, Спачвански базен) is a geographic microregion in eastern Croatia and northwest Serbia. The region is located in the south-western part of Syrmia—the latter being divided by Croatia and Serbia—and the southeastern part of Slavonia macroregion of Croatia, surrounding the Spačva river and the Studva river. The entire region is 51.000 hectares big out of which 40.000 is located in Croatia and 11.000 in Serbia.