National Route 9 (Vietnamese: Quốc lộ 9 (or abbrv. QL9) or Đường 9) runs across Vietnam roughly in line with the 17th Parallel. The route includes two segments. The segment called National Route 9A begins at Đông Hà and ends at Lao Bảo on the Vietnam-Laos border and is entirely within Quảng Trị Province. The 8 km-long segment called National Route 9B begins at Dong Ha and runs eastward to Cửa Việt Port.
Route 9 runs through the following towns and cities of Quảng Trị Province:
Route Coloniale 9 or RC9 was constructed by the French in the early 20th century.
In the early 1960s as the Vietnam War began to increase in intensity, the Army of the Republic of Vietnam (ARVN) and US Special Forces began to build a chain of bases south of the DMZ to interdict the flow of men and materiel from North Vietnam. These bases included:
Route 9 became a vital supply artery to these bases and the North Vietnamese Army (NVA) were frequently able to cut or ambush Route 9 during the "Border Battles" period from 1967 to 1969. Route 9 was the access road used in Operation Pegasus and Operation Lam Son 719.
In recent years with the implementation of Vietnam's Doi Moi reforms there has been an increase in cross-border trade with Laos and Route 9 has been progressively upgraded. With the completion of the Ho Chi Minh Highway, Route 9 has become an important link between the Ho Chi Minh Highway and Route 1.