Mainland Southeast Asia and the Mekong River

Mainland Southeast Asia — sometimes called the Indochina Peninsula, a name reflecting the region's historical position between Indian and Chinese cultural spheres — comprises Myanmar, Thailand, Laos, Cambodia, Vietnam, and peninsular Malaysia, and is physically distinct from the island nations of maritime or insular Southeast Asia. The region's geography is dominated by a series of roughly north-south trending mountain ranges, including the Arakan Yoma in western Myanmar and the Annamite Range (Truong Son in Vietnamese) running along the Vietnam-Laos border, which separate the major river valleys that have historically structured settlement, agriculture, and political organization across the peninsula.