Thung Salaeng Luang National Park (Thai: อุทยานแห่งชาติทุ่งแสลงหลวง, RTGS: Utthayan Haeng Chat Thung Salaeng Luang) is a 1,262 square kilometres (487 sq mi) national park in Phitsanulok and Phetchabun Provinces of Thailand.

Thung Salaeng Luang was declared the 3rd national park in 1963, covering an area of 1,282 square kilometres (495 sq mi).

At the request of the Thai Army 20 square kilometres (7.7 sq mi) were withdrawn from the national park.

Thung Salaeng Luang was "reestablished" as a national park on 27 May 1975, covering an area of 789,000 rai ≈1,262 square kilometres (487 sq mi).

[7] Communist insurgents as well as hill tribes and other intruders have destroyed some of the park's flora and fauna over the years.