The Río Negro is the main river of Patagonia in terms of drainage basin size and flow rate in eastern Patagonia. It originates at the confluence of the Limay River and the Neuquén River at the border with Neuquén Province, then flows southeast through Patagonian steppe for approximately 635 kilometers before emptying into the Atlantic Ocean near El Cóndor beach resort, roughly 30 km downstream from Viedma, the provincial capital. The river's name derives from the Mapuche term Curú Leuvú, though the water itself tends toward green rather than black. It was historically also called Río de los Sauces for the abundant weeping willows lining its lower course.

The lower 400 km of the river are navigable, making this stretch the primary zone of interest for paddlers. The river passes through open Patagonian steppe, a landscape defined by wide skies and sparse vegetation, with weeping willows providing notable riparian character along the lower reaches. The river's course passes near or through several population centers, including Villa Regina, and terminates near the twin cities of Viedma and Carmen de Patagones.

The Regata del Río Negro, held on this river, is recognized as the longest kayak race in the world, which speaks to the river's suitability for extended flatwater paddling expeditions. Kayakers regularly complete the full length of the river, and there is a strong tradition of paddlers navigating the river over multi-day journeys. The river's character across its navigable lower section is that of a large, flatwater Patagonian river crossing open steppe terrain.

Given the river's length and the scale of the navigable section, multi-day expeditions are the natural format for paddling here. The river's size and the surrounding agricultural and steppe landscape define the experience — this is a long-distance, open-water undertaking rather than a technical whitewater run.