The province includes the Annamite Range, stretching east to Vietnam, while to the west are the Mekong River and Thailand.

At 3,700 square kilometres (1,400 sq mi), the Nakai-Nam Theun National Park in Bolikhamsai and Khammouane provinces is the third largest protected area in Laos.

[5] After 1865, the invasions of "Hos", Chinese gangs from southern China, affected the provinces of Xieng Khouang and Bolikhamsai (Borikhane).

In the 1890s, Christian missionaries of the Missions étrangères de Paris arrived on the Mekong River, a few miles from the mouth of the Nam Sane.

The province includes the Annamite Range, stretching east to Vietnam, while to the west are the Mekong River and Thailand.

[9] The principal river is the Nam Kading, meaning 'water like a bell', a tributary of the Mekong; its catchment covers about 92% of the provincial area.

[2] At 4,270 square kilometres (1,650 sq mi), Nakai-Nam Theun National Park in Bolikhamsai and Khammouane provinces is the third largest protected area in Laos.

[11] The wetlands of the Nam Kading National Protected Area and the Phou Khao Khouay National Protected Area attract numerous migratory birds, and also has some 13 globally and 12 regionally endangered mammals such as the Asiatic black bear, clouded leopard, elephant, giant muntjac, gaur, sun bear, and tiger and both northern and southern white-cheeked crested gibbon.

The saola (spindle horn) or Vii Quang ox (Pseudoryx nghetinhensis) was discovered in neighbouring Vietnam in 1992 and sighted since then in this conservation area.

[citation needed] Under the World Wildlife Fund (WWF) Greater Mekong Lao PDR Country Programme, studies have been carried out in the two forest areas in the province to assess the degree of sustainable rattan harvest and production as it provides significant income in whole of the Mekong region to rural villages.

[11] The province is made up of the following districts:[2] Laos's largest hydroelectric project, Nam Theun 2 Dam (NT2), began operation in March 2010.