The largest island in the Koh Chang Marine Park archipelago, Ko Chang was named for the elephant shape of its headland, although elephants are not indigenous to the island.

Koh Chang has an area of approximately 429 square kilometres. The topography contains high mountains and complex stone cliffs. The highest mount is Khao Salak Phet which is 744 metres high, rich in fertile evergreen forest which is the main water source. Therefore, there are many waterfalls, beaches and splendid reefs in the west of the island.

Most accommodation is located on the western side of the island, where the sandy beaches are. On the eastern side of the island there are no sandy beaches and this side is far less touristy. There are some nice waterfalls.
70 percent of this undisturbed island is rainforest, steep hills, cliffs, waterfalls, and wildlife, fine beaches, coral reefs and an abundance of marine life. The island also offers tall mountains and rock cliffs. The tallest mountain on Ko Chang is Salakpetch.