Guatuso is the name of the 15th canton in the province of Alajuela in Costa Rica. The canton covers an area of 758.32 square kilometres (292.79 sq mi), and has a population of 13,984 (estimate as of 2003). The capital city of the canton is San Rafael de Guatuso.
It is a diamond-shaped canton, with the Río Purgatorio (Purgatory River) and the Río Frío (Cold River) as the northeast border, the Río Cucaracha (Cockroach River) as a portion of the southeast border, the Cordillera de Guanacaste on the southwest border, and the Río Rito and the Río Mónico on the northwest. Tenorio Volcano marks the far western point of the canton.
The canton of Guatuso is subdivided into four districts (distritos):
San Rafael, Buenavista, Cote, Katira
The canton was established by a decree of March 17, 1970. It is named for the region's original inhabitants, an indigenous tribe whose survivors are now known as the Maleku and remain as residents of the area.