Fortín San Juan de la Cruz (Fort Saint John of the Cross), better known as el Cañuelo, is located on Isla de Cabras , Puerto Rico, at . It is part of San Juan National Historic Site.

The square fort is about 80 feet (24 m) per side, with one guerite (guerita). Originally built on a rocky islet, nearby Isla de Cabras (Goat Island) was artifically expanded to incorporate it. El Cañuelo guarded the mouth of the Bayamón River —but more importantly it filled a gap in the artillery coverage from Fort San Felipe del Morro of the entrance to San Juan Bay.

Although difficult for tourists to find, the site features fabulous views of Boca Vieja Cove to the west and San Juan Bay to the east. The fort inself is closed to the public, but one can walk around it. Isla de Cabras has small sandy beaches, and is connected to the main island by a short bridge. The nearby village of Palo Seco features many good restaurants.