Rio Piquiri is a significant river system flowing through the state of Paraná in southern Brazil, draining into the upper Paraná River basin. As part of the Piquiri sub-ecoregion, this river and its tributaries support a remarkable diversity of freshwater fish — with the sub-ecoregion documented to harbor approximately 154 species. The river winds through a landscape shaped by the geology of the upper Paraná basin, with its headwaters and low-order tributary streams providing critical habitat for a wide range of species, including some that are rare, endangered, migratory, endemic, and even undescribed by science. The Piquiri basin is recognized as one of the most biologically important river systems in Paraná, and its integrity is considered essential for the persistence of regional aquatic biodiversity.