Nattai is a national park in New South Wales (Australia), 150 km southwest of Sydney. It is part of the Greater Blue Mountains World Heritage Area, and primarily encompasses the valley of the Nattai River, which is surrounded by spectacular sandstone cliffs. The park is covered in dry sclerophyll (hard leafed) forest - mostly eucalypt, and has fairly frequent forest fires. It is largely an untouched wilderness area.
The park adjoins the Kanangra-Boyd National Park (which is to the north). Lake Burragorang (water supply for Sydney) also borders the northern side of the park, and there is a 3 km exclusion zone surrounding into which entry is prohibited. The Nattai receives very few visitors, as it has virtually no facilities and is fairly remote, despite its proximity to Sydney.