Río Manso Superior is the uppermost section of the Manso River system, born from the Manso Glacier and flowing down through the rugged Patagonian landscape of Río Negro, Argentina, before emptying into the northwest shore of Lago Mascardi within Nahuel Huapi National Park. Its waters are characteristically glacial — cold, turbid, and heavily laden with glacial sediment — giving the river a distinctive milky-blue appearance that sets it apart from the clearer reaches downstream. This headwaters section flows through some of the most dramatic and remote terrain in Argentine Patagonia, surrounded by old-growth forests and towering Andean peaks. While fishing is not permitted in the Manso Superior itself, the delta where it meets Lago Mascardi is a well-known and productive hotspot that draws anglers from across the region. The broader Manso River system is accessible from November 1st through May 1st, with the summer months offering the most consistent fishing conditions.