Koh Lanta Yai is an island in the Lanta Islands National Park in Koh Lanta Yai Subdistrict, Koh Lanta District, Krabi Province. It is home to the district office and the park office. It is a complex mountain range covered with pristine forest.

The name “Lanta” is believed to have been distorted from the Javanese word “Lantas”, which means a place to grill fish, because in the past it was a place where Javanese sailors often stopped to rest and grill fish for food.

Koh Lanta Yai is approximately 30 kilometers long and 6 kilometers wide. There are 13 long beaches on the west coast, both rocky and sandy.