Friendship Pass (traditional Chinese: 友誼關; simplified Chinese: 友谊关; pinyin: Yǒuyì Guān; Cantonese Jyutping: Jau5 Ji4 Gwaan1; Cantonese Yale: Yau5 Yi4 Gwaan1; Vietnamese: Hữu Nghị Quan), also commonly known by its older name Ải Nam Quan (隘南關), is a pass near the border between China's Guangxi and Vietnam's Lạng Sơn Province, on the Chinese side of the border (21°58′35″N 106°42′44″E). Vietnamese National Route 1A starts near to this pass, which lies less than 5 km north of the town of Đồng Đăng in Lạng Sơn Province, ending in Năm Căn in Cà Mau Province. China National Highway 322 runs from here to Guangxi Province and Hunan Province. This is one of the busiest border trading points of Vietnam.
It was built in the early Ming dynasty with the name of "South Suppressing Pass" (traditional Chinese: 鎮南關; ; pinyin: Zhèn Nán Guān; Cantonese Yale: Jan3 Naam4 Gwaan1; Vietnamese: Trấn Nam Quan). In 1953, its name was changed to "South Watching Pass" (traditional Chinese: 睦南關; simplified Chinese: 睦南关; pinyin: Mù Nán Guān; Cantonese Yale: Muk6 Naam4 Gwaan1; Vietnamese: Mục Nam Quan). In 1965, its name was changed again to the current Friendship Pass, reflecting the close political, military, and economic ties between the People's Republic of China and North Vietnam during the then-ongoing Vietnam War.
Traditionally, the pass served as the exact border between China and Vietnam, hence there is also a Vietnamese historical saying: "Nước Việt Nam ta trải dài từ Ải Nam Quan đến mũi Cà Mau," translated as "The Vietnamese nation stretches from Ải Nam Quan to Cape Cà Mau". However, recently the pass has been in Chinese control and well within Chinese territory, in Pingxiang, Chongzuo County, Guangxi Autonomous Region, since the early 1950s, and the official border between the two nations is beyond this pass. The new border was later confirmed by Chinese and Vietnamese communist officials by a border treaty enacted in June 2000, with Vietnamese officials stating that some Vietnamese territory along the Sino-Vietnamese border, namely in Cao Bằng Province and Lạng Sơn Province has been ceded to China. This concession met with an uproar among the Vietnamese populace.