Quảng Bình province in the context of North Central Coast

Đàng Ngoài (chữ Hán: 唐外, lit. "Outer Land"), also known as Bắc Hà (北河, "North of the River") or Kingdom of Annam (安南國) by foreigners, was an area in northern Đại Việt (now Vietnam) during the 17th and 18th centuries as the result of Trịnh–Nguyễn War. The name Đàng Ngoài was first recorded in the Dictionarium Annamiticum Lusitanum et Latinum by Alexandre de Rhodes.

Đàng Ngoài was de facto ruled by the Trịnh lords with the Lê emperors acting as titular rulers. The capital was Thăng Long (now Hanoi). Thăng Long was also known as Đông Kinh 東京, meaning "Eastern Capital", from which the common European name for Đàng Ngoài "Tonkin" originated. It was bordered by Đàng Trong (under the Nguyễn lords) along the Gianh River in Quảng Bình province. The names gradually fell into disuse after Nguyễn Ánh reunified Đại Việt.

Võ Nguyên Giáp (chữ Hán: 武元甲, Vietnamese pronunciation: [vɔ̌ˀ ŋʷīən jǎːp]; 25 August 1911 – 4 October 2013) was a Vietnamese general, communist revolutionary and politician. Highly regarded as a military strategist, Giáp led Vietnamese communist military forces to victory in the decades long Indochina wars. Giáp was the military commander of the Việt Minh and the People's Army from 1941 to 1972, minister of defense of the Democratic Republic of Vietnam (North Vietnam) and the Socialist Republic of Vietnam in 1946–1947 and from 1948 to 1980, and deputy prime minister from 1955 to 1991. He was a member of the Politburo of the Communist Party of Vietnam.

Born in Quảng Bình province to an affluent peasant family, Giáp began participating in anti-colonial political activity in 1925. Sources conflict as to whether he joined the Indochinese Communist Party in 1930, or not until 1940. Giáp rose to prominence during World War II as the military leader of the Việt Minh resistance against the Japanese occupation, and after the war led anti-colonial forces in the First Indochina War against the French. He won a decisive victory at the 1954 Battle of Dien Bien Phu, which ended the war. In the Vietnam War, Giáp led the PAVN against South Vietnam and the United States. Giáp was commander of the army during the 1968 Tet Offensive and 1972 Easter Offensive, after which he was succeeded by Văn Tiến Dũng, but remained defense minister through the U.S. withdrawal and final victory against South Vietnam in 1975. Giáp oversaw his final campaigns in the successful Vietnamese invasion of Cambodia in 1978 and the 1979 Sino-Vietnamese War. He resigned as defense minister in 1980 and left the Politburo in 1982. Giáp remained on the Central Committee and as deputy prime minister until 1991, and died in 2013 at age 102.

The Gianh River (vernacular Vietnamese: sông Gianh, also known as Gianh giang; Sino-Vietnamese: Linh Giang 靈江) is a river in the Quảng Bình province of Vietnam's North Central Coast (Bắc Trung Bộ). The river is 268 kilometres (167 mi) in length.

The Gianh–Son River served as the boundary between Đàng Ngoài and Đàng Trong, ruled by rival families, during the partition of Vietnam in the 17th and 18th centuries following the Trịnh–Nguyễn War. The 17th parallel, used as the border between North Vietnam and South Vietnam from 1954 to 1975, was located just south of the Gianh River, at the Bến Hải River in Quảng Trị province.

Quảng Trị (Vietnamese pronunciation: [kʷâŋ ʈ͡ʂîˀ]) is a coastal province near the southernmost part of the North Central Coast region, the Central of Vietnam. It borders Huế to the south, Savannakhet of Laos to the west and the South China Sea to the east, with 75 kilometres (47 mi) of coast. On June 12, 2025, Quảng Bình province was merged into Quảng Trị.