Than Sadet – Ko Pha-ngan (Thai: ธารเสด็จ-เกาะพะงัน) is a national park in southern Thailand, protecting 65.93 km (25.46 sq mi) mostly on the island Pha Ngan. The park was established on December 31, 1983, covering an area of 39.12 km2 (15.10 sq mi), and was enlarged to its present size on February 10, 1999.