Ko Tarutao island (Thai: เกาะตะรุเตา) is the largest island of Tarutao National Marine Park in Satun Province province of Thailand, close to Malaysia border. The island is 26 km long and 11 km wide. It is one of the most unspoiled islands in Andaman Sea and in all of Thailand. The Malay word tertua or tarutao means old and primitive.
There is a concrete road running through the island, but the terrain is rugged and mountainous with several peaks stretching more than 500 metres high. The highest peak is 713m high. Most of the island territory is covered in dense, old growth jungle. Mangrove trees and limestone cliffs cover much of the island shores. The western coast has long and wide white-sand beaches which are historical nestling ground sites for turtles. Langurs, crab-eating macaques and wild pigs are common on the island.
Ao Son beach on the west side of the island is over 4 km long and over 200 m wide.
From its eastern side the larger island of Ko Tarutao is encircled by over 10 smaller offshore islands and limestone karst islets, such as Ko Sing, Ko Kaman, Ko Ko Lo, Ko Klang, Ko Pulao Na, Ko Daeng, Ko Laen, Ko Lek, and others.