Guapiaçú River

The Guapiaçú River (Rio Guapiaçú, sometimes Guapi-Áçu River) is a river of Rio de Janeiro state in southeastern Brazil. It is a tributary of the Macacu River.

The Guapiaçú River forms part of the eastern boundary of the 15582 ha Guapi-Guapiaçú Environmental Protection Area, created in 2004. It rises in the Serra do Mar between Nova Friburgo and Cachoeiras de Macacu. In its lower reaches, it defines the boundary between the municipalities of Cachoeiras de Macacu to the east and Guapimirim to the west.