Rio Sepotuba is a river flowing through Mato Grosso, Brazil, draining into the upper Rio Paraguai basin — the vast fluvial system that feeds the legendary Pantanal wetlands. The river is part of a critical network of waterways that includes the Rio Paraguai, Rio Cabaçal, Rio Jauru, and Rio do Sangue, all of which share ecological and hydrological connectivity. The Sepotuba basin is recognized as one of the areas of greatest longitudinal connectivity in the upper Paraguay system, making it especially important for migratory fish species that move upriver to spawn. The river ranges from headwater streams in the highlands near Tangará da Serra to broader, slower reaches as it approaches its confluence with the Rio Paraguai. This diversity of habitat — from fast-moving headwater riffles to deeper main-channel pools — supports a rich and varied fish community.