The Guadiaro is a river in the Spanish provinces of Cádiz and Málaga in the autonomous community of Andalusia, Spain. It flows southward from the Sierra Bermeja through the Sierra de Grazalema and discharges into the Mediterranean at Sotogrande. The river is notable for having some of the only marshland on the Costa del Sol. This marsh is protected by a 27 hectares nature preserve. There are several towns and communities near its mouth, Pueblonuevo de Guadiaro, Guadiaro, Torreguadiaro, Sotogrande, San Enrique, and Venta Nueva, all located within the San Roque municipality.