The Arroyo del Medio is a 62-kilometer stream located in the departments of Cainguás and Oberá in Misiones Province, northeastern Argentina. It originates in the watershed divide of the sierra de Misiones within the municipality of Campo Grande, at an elevation of approximately 450 meters above sea level, and descends to its mouth at roughly 140 meters above sea level where it joins the Arroyo Acaraguá near the municipal balneario of Campo Ramón.

In its upper reaches, the stream descends gradually across the central plateau, crossing Ruta Nacional 14 at kilometer marker 909.5. After this crossing, it receives the waters of the Arroyo Aguas Dulces on its left bank. The stream initially runs on a northwest-to-southeast orientation before shifting to a southward course. As it progresses, the valley becomes increasingly sinuous and the channel progressively deeper, eventually taking on a confined, canyon-like character. Along this lower section, the Arroyo de la Cruz and the Arroyo Yazá enter from the right bank.

Among its principal right-bank tributaries are the arroyos de la Cruz, Yazá, and Persiguero; left-bank tributaries include the arroyos Padilla, Grapia, Aguas Dulce (also known as Chiquero), Rosa, Tarumita, and Tres Pasos. A municipal balneario at Campo Ramón near the confluence with the Arroyo Acaraguá provides public access and recreational use in that area.