Llancahue
{{distinguish|Llancahue River}}
{{Use dmy dates|date=May 2025}}
{{Infobox Protected area
| name = Llancahue Nature Sanctuary
| alt_name = Reserva Periurbana Llancahue
| iucn_category =
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| photo =
| photo_caption =
| map = Chile
| map_alt =
| map_caption = Location in Chile
| map_width =
| relief = 1
| location = Los Ríos Region, Chile
| nearest_city = Valdivia
| coordinates = {{coord|39|49|0|S|73|07|0|W|display=inline, title}}
| area_km2 = 12.77
| designated = 2022
| designation = Nature sanctuaryUNEP-WCMC (2023). [https://www.protectedplanet.net/555745179 Protected Area Profile for Llancahue] from the World Database on Protected Areas, May 2023.
| visitation_num =
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| governing_body = Austral University of Chile
}}
Lancahue is a protected area and watershed in the commune of Valdivia, Chile. It has an area of 12.7 km2, of which 7 km2 are old-growth forest.{{Cite journal |title=Balancing water supply and old-growth forest conservation in the lowlands of south-central Chile through adaptive co-management |journal=Landscape Ecology |url=https://link.springer.com/article/10.1007/s10980-013-9969-7 |last=Donoso |first=Pablo J. |volume=29 |pages=245–260 |last2=Frêne |first2=Cristián |year=2014 |last3=Flores |first3=Marco |last4=Moorman |first4=Michelle C. |last5=Oyarzún |first5=Carlos E. |last6=Zavaleta |first6=Jennifer C.}}{{Cite journal |title=Cambios en cobertura y regeneración arbórea en bosques siempreverdes en diferentes estados sucesionales en el sitio experimental de Llancahue, Cordillera de la Costa de Valdivia, Chile |journal=Gayana. Botánica |url=https://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-66432018000200657&lng=es&nrm=iso&tlng=es |last=Donoso |first=Pablo J. |issue=2 |volume=75 |last2=Diego B. |first2=Ponca |last3=Pinto |first3=Joselyn B. |last4=Triviño |first4=Iván L.|year=2018 |language=Spanish |trans-title=Changes in cover and tree regeneration in evergreen forests in different successional stages in the Llancahue experimental site, Coastal range of Valdivia, Chile|doi=10.4067/S0717-66432018000200657|doi-access=free }} The protected area host a relatively unscathed remnant of lowland (<300 m asl.) Valdivian temperate forest. Part of the protected area contain secondary forest that started to develop after a fire around 1914, while other secondary forests originated from intense wood logging.González, M.E., Szejner, P., Donoso, P.J., Salas-Eljatib, C. (2015). Fire, logging and establishment patterns of second- growth forests in south-central Chile: implications for their management and restoration. Ciencia e Investigación Agraria 42(3): 427-441
The main tree species in Llancahue are Nothofagus dombeyi, Eucryphia cordifolia, Laureliopsis philippiana and Aextoxicon punctatum.{{Cite web |url=http://vinculacion.uach.cl/index.php/comunicaciones/16-noticias/cientificas/749-llancahue-agua-conservacion-y-selva-valdiviana |title=Llancahue: agua, conservación y selva valdiviana |date=2013-03-11 |access-date=2023-04-26 |website=Dirección de vinculación con el medio |publisher=Austral University of Chile |language=Spanish}}
The drainage basin of Llancahue is used for water supply in the nearby city of Valdivia.