The Rio das Mortes — whose name translates to "River of the Dead" — is a significant river system flowing through Mato Grosso state in western Brazil, stretching approximately 580 kilometers (360 miles) before reaching its mouth near coordinates 11°44′S 50°43′W. This river drains a portion of the Cerrado biome, Brazil's vast tropical savannah, and its basin supports one of the most biodiverse freshwater fish assemblages in the world. The Rio das Mortes basin is part of the broader Araguaia River system and is characterized by remarkable ichthyological richness, with scientific surveys of its headwater streams alone documenting representatives from six orders, 20 families, 52 genera, and 77 species — with roughly 51% of those species found exclusively within the Rio das Mortes drainage. Tributaries of the river are known for crystal-clear water, sandy bottoms, leaf litter, and submerged root systems, creating a diverse and productive aquatic environment for both fish and anglers.