The Río Gualeguay is one of the major rivers of Entre Ríos Province, running approximately 350 to 375 kilometres in a general south-southwestward direction through the center of the province. Its source lies in the north, in the region between Federación and San José de Feliciano, and it passes through or near the cities of Villaguay, Rosario del Tala, and Gualeguay before emptying into the Río Paraná Ibicuy, a distributary of the Paraná River in the Paraná Delta. The river's drainage basin covers roughly 22,716 square kilometres, occupying a depressed corridor between the low hill systems of the Cuchilla de Montiel to the west and the Cuchilla Grande to the east. Average discharge measured between 1964 and 1968 was approximately 210 cubic metres per second.

The river has a notably serpentine character, with frequent and pronounced bends that define the paddling experience. The water carries a muddy, turbid appearance and moves with some pace. The river is accessible from the Río Paraná end, and the docks along the Gualeguay are roughly a three-hour drive from Buenos Aires.

The Gualeguay supports a diverse and notable fish population, including golden dorado, wolf fish, and piranhas — a combination that warrants awareness for paddlers who may be wading or swimming. Fishing, particularly for golden dorado, is an established activity on the river and draws visitors specifically for that purpose. Paddlers should be aware that motorized skiffs operate on the river as part of fishing and touring operations.