Alerce Costero National Park, National park in El Ranco Province, Chile.

Alerce Costero National Park lies in La Unión commune, Los Ríos Region, and covers 2,308 hectares in two units: Altos del Mirador (1,406 ha) and Chaihuín (902 ha). Its altitude ranges from 650 to 1,048 m. The park protects alerce, canelo, Guaitecas cypress, tineo and Chiloé coigüe, and is home to güiña, puma, quique, pudú and black woodpecker.

The area was created on 3 January 1987 by Chile's Ministry of National Assets as the Alerce Costero Natural Monument, covering 2,308 hectares split between the Altos del Mirador (1,406 ha) and Chaihuín (902 ha) units. In 1996 CONAF listed it in its red book of priority sites, and in 2012 it was folded into the new Alerce Costero National Park.

The park's name comes from the alerce, a slow-growing conifer whose wood was long prized for roof shingles. The Alerce Milenario trail leads to a specimen 4.26 m in diameter, and along the route stand burned alerce trunks still upright. The area was created on 3 January 1987 by the Ministry of National Assets and became part of Alerce Costero National Park in 2012.

The park can be explored on foot or by bicycle, with multiple entry points providing access to different areas. It is helpful to prepare for damp forest conditions and bring appropriate gear for outdoor activities.

The Alerce Milenario trail, 2 km from the CONAF ranger station, leads to an alerce whose trunk measures 4.26 m in diameter. Nearby stand burned alerce trunks still upright, remains of past fires in these forests.