Santuario de la naturaleza Humedal Río Maipo, Wetland nature reserve in Valparaíso Region, Chile

The Maipo River Wetland Sanctuary is a protected natural reserve combining saltwater marshes and freshwater lagoons in the Valparaíso Region. The site stretches along the river with dense vegetation, reeds, and open water areas connected by pathways and observation platforms for visitors.

The Maipo River estuary was listed as a priority conservation site in 2007 and declared an Important Bird Area by BirdLife International in 2010. In 2015 the Hemispheric Network of Shorebird Reserves recognised it for its pilpilén and whimbrel populations. On 27 January 2020, Decree No. 1/2020 of the Ministry of the Environment declared the 60.3-hectare wetland a Nature Sanctuary.

The park takes its name from the pilpilén, the oystercatcher that forages on the estuary flats. Its first bird observatory, the Mirador Pilpilén, was built after the municipality's agreement with the ECIM of the Pontificia Universidad Católica and follows Wildfowl & Wetlands Trust design guidelines. Since 2014 the Fundación Cosmos has run environmental education programmes and birdwatching tourism here.

Access is via marked wooden boardwalks that remain walkable in wet conditions and accommodate different mobility levels. Visitors should wear weather-appropriate clothing and closed shoes since the terrain is marshy and insects are common during warm months.

The site hosts nearly 200 bird species, including rare migrants that regularly stop here during their long journeys between North and South America. This role as a resting point makes it a top destination for observers wanting to see traveling birds across different seasons.