Rio Preto is a tributary of the middle course of the Rio Paraíba do Sul, flowing through the state of Rio de Janeiro in southeastern Brazil under the influence of the Serra da Mantiqueira mountain range. As part of the Middle Rio Paraíba do Sul bioregion, this river is embedded within the Atlantic Forest landscape and is recognized for its notable freshwater fish diversity, particularly among small-bodied native species adapted to the clear, fast-moving waters typical of mountain tributaries in this region. The river's position within this bioregion places it among a network of ecologically significant streams that collectively support one of the more diverse freshwater fish assemblages in the state.