Estero De Catapilco is a natural watercourse in the Valparaíso Region of Chile, approximately 26 km in length, draining a watershed of roughly 318 km². It originates near the city of Catapilco at the confluence of Estero de la Retamilla, arriving from the northeast, and Estero Blanquillo, arriving from the east and south. From there it flows in a generally southwestward direction, with frequent changes in course, before emptying into the Pacific Ocean at the cove of Maitencillo. Along its lower reach, the estero forms a lagoon adjacent to the resort area of La Laguna de Zapallar, which takes its name from this feature.

The lower lagoon and estero together constitute a declared Urban Wetland — officially named Laguna y Estero Catapilco — spanning approximately 10.45 hectares across the comunas of Puchuncaví and Zapallar. This wetland is classified as a natural, lacustrine, estuarine, and riparian permanent system, and it falls entirely within the urban boundary. It provides habitat for several endemic fish species of conservation concern, including Cheirodon pisciculus, Basilichthys australes, and Odontesthes brevianalis.

The wetland has been identified as threatened by unregulated tourist and recreational activities, which is a consideration for anyone planning to paddle in the area. Prospective paddlers should verify current regulations with Chilean environmental authorities before visiting, as the protected status of the wetland may impose restrictions on recreational use.