Sa Mu Pass is a pass on the Ho Chi Minh Trail in the border area of ​​Huong Phung and Huong Viet communes, Huong Hoa district, Quang Tri province, Vietnam. The pass is located at the intersection of different weather zones of the east and west of Truong Son, so it often has cool temperatures and a magical sea of ​​clouds. The name of the pass is named after Xe Samu stream, the stream originating from the western back of the pass. This is a river about 43 km long, belonging to the Mekong River basin. The river flows west into Laos, and flows into Se Banghieng in Vanghai village. However, due to the magical sea of ​​clouds that often appears, tourists interpret the name "Sa Mu" as "falling misty clouds".