The Valdes Peninsula (Spanish: Península Valdés) is a peninsula into the Atlantic Ocean in the Viedma Department of north-east Chubut Province, Argentina. Around 3,625 km² (896,000 acres; 1,400 sq mi) in size (not taking into account the isthmus of Carlos Ameghino which connects the peninsula to the mainland), it is an important nature reserve which was listed as a World Heritage Site by UNESCO in 1999.