he Si Phan Don (Lao: ສີພັນດອນ; meaning The 4000 islands) is a riverine archipelago located in the Mekong River, Champasak Province in southern Laos. Si Phan Don is characterised by numerous islands, half of which are submerged when the Mekong River is in flood. The principal islands of Si Phan Don are Don Khong (the largest), and Don Det and Don Khon.