Laguna Melincué is a large endorheic lake located in the General López Department of Santa Fe Province, Argentina, adjacent to the town of Melincué at approximately 33°42′S, 61°29′W. The lake covers roughly 120 square kilometers and sits at an elevation of around 82–86 meters above sea level. As an endorheic basin with no outflow, water levels can fluctuate significantly, and during drought periods the lake's waters become saline, giving it a characteristic brownish coloration. These large surface oscillations have historically influenced salinity levels throughout the lake.

The waters are notably shallow and flat across their expanse, making the lagoon well-suited for flatwater paddling disciplines such as stand-up paddleboarding. The consistent pampa winds that sweep across the region make it a popular destination for kitesurfing and wingfoiling as well, so paddlers should be aware of wind-driven chop and the presence of other water users, particularly kite surfers. Paddlers should also note that wooden fences exist in some areas of the shoreline, and debris on the beach warrants care when launching.

The lagoon was designated a Ramsar Wetland of International Importance in July 2008, covering a protected area of 920 square kilometers. This recognition reflects the lake's ecological significance as a wetland ecosystem supporting large populations of waterfowl and other birds, including flocks of flamingos. Reed beds, totora sedge banks, chañars, and espinillos characterize the surrounding vegetation. Islands are visible on the lake's surface, and one of them holds the ruins of an old hotel abandoned after two floods, a notable landmark for paddlers exploring the area.

The lake has a warm and humid climate. Access to the lagoon is public, and the site can be reached from Buenos Aires via Ruta Nacional 9 and Ruta Provincial 90, a distance of approximately 362 kilometers. Ruta Provincial 93 and Ruta Provincial 90 provide local access. The town of Melincué, situated directly beside the lagoon, offers visitor amenities including thermal baths and a casino. A recommended stay of two to three days allows adequate time to explore the lake and surrounding wetland reserve.

Laguna Melincué has historically been recognized as one of the better fisheries in the region for pejerrey (Odontesthes bonariensis), particularly noted for the size of fish caught, which means fishing activity is present on the water.