Helicopters of Vietnam: 1946-1969
While the H-13, the H-21, and the H-34 were developed by the US Armed Forces prior to the Vietnam War, and would eventually see use in Vietnam and throughout Southeast Asia, most of these helicopters were developed and adopted for explicit use in Vietnam, and saw extensive action throughout the conflict.
This list is by no means exhaustive; instead, it is meant to highlight some of the most influential and long-lasting American helicopters of the Vietnam War, and to encourage further research.