Río Cuchildeo is a short river in the Los Lagos Region of Chile, approximately 5 km in length. It originates on the southern slopes of Volcán Hornopirén and flows southward before emptying into the northern section of Canal Hornopirén, on the western edge of the town of Hornopirén. It is one of three rivers that flow through or alongside Hornopirén, the others being Río Negro and Río Blanco.

The river is classified as a ritron type, meaning it is a fast-flowing watercourse with a rocky substrate. Its average width is around 6 m, though this varies considerably depending on conditions and season. During winter periods, widths of 15–20 m have been recorded, while some sections narrow to less than 4 m. Current speeds average between 1 and 2 m/s, and the mean annual discharge is 17 m³/s. These characteristics — a swift, relatively narrow channel with variable width — suggest a dynamic river environment that would require attentiveness to changing hydraulics, particularly in constricted sections.

Given its short length and the proximity of Hornopirén at its mouth, the river is geographically accessible from the town. However, designated put-in or take-out points, portages, known hazards, paddling regulations, and facilities for paddlers have not been documented.