Arroyo Mbocay is a tributary stream located in the Puerto Iguazú area of Misiones Province, Argentina, flowing within the broader Paraná River basin. The stream is notable for its position within — or adjacent to — one of the most biologically rich protected areas in South America, and it sits at the intersection of the Lower Paraná ecoregion, a zone recognized for its remarkable ichthyological diversity. The arroyo crosses Ruta 12, a key access corridor in the region, and its waters drain into the Paraná watershed, making it part of a vast and ecologically significant river system. The surrounding landscape is characterized by the subtropical Atlantic Forest, one of the most biodiverse ecosystems on the planet, which directly influences the stream's ecology, water chemistry, and the fish communities it supports.