The Tunasan River, also referred to as the Tunasan–Cuyab River, is a river system in the Philippines. The river begins at the border of San Pedro, Laguna and Dasmariñas, Cavite, and ends 9 km at the border of San Pedro and Muntinlupa. It is one of 21 major tributaries of Laguna de Bay. The river system has six adjoining creeks: one in San Pedro, Laguna, one in Dasmariñas, Cavite, three from the ponds of Hallow Ridge Filipinas Golf in San Pedro, and one from the drainage system of RMT Complex in Muntinlupa. The depth of the Tunasan River currently varies from 0.25 to 2 m. Both the river and barangay Tunasan were named after a medicinal plant locally called tunas (Nymphaea nouchali), once abundant on the Tunasan River and the shoreline of Laguna de Bay. The Tunasan River received media attention in 1994 and 1995 due to a series of "fish kills" caused by high biochemical oxygen demand from decomposing water lilies and the profusion of residential wastes that find their way into the river during the rainy season.