Guaporé River (Portuguese: Rio Guaporé, Spanish: Río Iténez) is a river in western Brazil and northeastern Bolivia. It is 1,260 km (780 mi) long; 920 km (570 mi) of the river forms the border between Brazil and Bolivia. The Guaporé River is part of the Madeira River basin, which eventually empties into the Amazon River. The Guaporé River crosses the eastern part of the Beni savanna region.It forms the border of the 615,771 hectares (1,521,600 acres) Guaporé Biological Reserve, and is fed by rivers originating in the reserve, the São Miguel, Branco, São Simão, Massaco and Colorado.