The Vietnamese Demilitarized Zone was established as a dividing line between North and South Vietnam as a result of the First Indochina War.

During the Second Indochina War (popularly known as the Vietnam War), it became important as the battleground demarcation separating North Vietnamese territory from South Vietnamese territory.

The Vietnamese Demilitarized Zone ran from east-west near the center of present-day Vietnam (spanning more than a hundred kilometers) and was a couple of kilometers wide. It ran along the Ben Hai River for much of its length, and an island nearby was controlled by North Vietnamese forces during the Vietnam War. Although it was nominally described as being at "the 17th parallel," almost all of the zone lies to the south of the parallel, with only a small portion of the zone near the eastern shore actually including the parallel.

It was around a hundred kilometers north of the city of Huế.

The First Indochina War (also called the French Indochina War) was fought in French Indochina from 1946 through 1954 between France and the French-controlled State of Vietnam on the one side, and the Communist-dominated independence movement, the Viet Minh, on the other. The Viet Minh won the war, gaining effective control of all northern Vietnam except an enclave around Hanoi.

In military terms, a demilitarized zone (DMZ) is an area, usually the frontier or boundary between two or more military powers (or alliances), where military activity is not permitted, usually by peace treaty, armistice, or other bilateral or multilateral agreement. Often the demilitarized zone lies upon a line of control and forms a de-facto international border.

Several demilitarized zones have also unintentionally become wildlife preserves, as they cause the land which they sit on to be too dangerous for construction and less exposed to human disturbance or hunting. See Korean Demilitarized Zone, Vietnamese Demilitarized Zone, Ben Hai River, Hien Luong Bridge

Generally, "demilitarized" means converted to non-military use or purpose, returned to a demilitarized field. In such meaning the term is often used in former Soviet republics both in Western and local (transliterated) languages.

Although many demilitarized zones are also neutral territory, since neither side is allowed to control it even for non combat administration, there are cases where a zone remains demilitarized after an agreement awarding full control to one state, which relinquished the normal right to establish any military forces or installations there.