The Rio Vacacaí-Mirim is a tributary river flowing through the state of Rio Grande do Sul in southern Brazil, forming part of the greater Jacuí river basin — one of the most ecologically significant drainage systems in the region. The river winds through a landscape typical of the Rio Grande do Sul interior, and its waters support a community of migratory and resident fish species that have long attracted local anglers and sustained traditional fishing communities along its banks. As part of the broader Jacuí basin network, the Vacacaí-Mirim shares hydrological and ecological connections with neighboring rivers including the Vacacaí, Taquari-Antas, Pardo, Pardinho, Sinos, and Caí, all of which drain into the main Jacuí channel. This interconnected system creates important corridors for migratory fish, making the Vacacaí-Mirim a meaningful destination for anglers targeting species that move through the basin seasonally.